J 


BBK 


NOTES 


ON  THE 

TREATMENT  OF  MERCURY 


IN 


NORTH  CALIFORNIA. 

BY 


T.  EGLESTON,  Ph.  D., 

COLUMBIA  SCHOOL  OF  MINES,  NEW  YORK  CITY. 


[FROM  VOL.  Ill  TRANSACTIONS  OF  THE  AMERICAN  INSTITUTE  OF  MINING  ENGINEERS.] 


PHILADELPHIA: 

SHEKMAN  & CO,  PRINTERS. 
1 8 7 6. 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/notesontreatmentOOegle 


NOTES  ON  THE  TREATMENT 


OF 

MERCURY  IN  NORTH  CALIFORNIA. 


The  ores  of  mercury  of  North  California  are  composed  of  metallic 
mercury  and  cinnabar.  They  are  found  in  serpentine,  and  are  very 
often  associated  with  chalcedony,  in  masses  more  or  less  irregular, 
often  concentrated  enough,  however,  to  furnish  ores  yielding  from 
three  to  ten  per  cent.,  and  sometimes  richer.  This  deposit  makes  its 
appearance  in  Vallejo  where  it  has  been  worked.  North  of  here 
the  mines  are  more  developed.  Most  of  the  quicksilver  mines,  how- 
ever, are  situated  in  Sonoma  and  Napa  Counties.  On  its  outcrop 
the  serpentine  rocks  have  become  decomposed,  and  have  often  been 
washed  away  to  a considerable  depth,  so  that  in  many  cases  in  their 
neighborhood,  what  is  apparently  nothing  but  ordinary  dirt,  will 
frequently  contain  from  two  to  three  per  cent,  of  metallic  mercury, 
with  but  a trace  of  cinnabar,  in  which  case,  as  at  the  Sonoma  mine, 
it  is  made  up  into  adobes  and  distilled.  Such  material  does  not 
require  to  be  mixed  with  dirt  to  be  made  into  adobes.  Very  often, 
also,  the  outcrop  of  the  rock,  where  it  is  not  decomposed,  is  filled  with 
metallic  mercury,  so  that  by  striking  a pick  into  it,  as  at  the  Rattle- 
snake mine,  a pound  or  more  of  mercury  at  a time  will  sometimes  spurt 
out.  Such  rock  as  this  is  found  in  several  localities  in  every  stage  of 
impregnation,  and  usually  makes  very  rich  ore.  There  is  generally, 
however,  very  little  of  it,  and  it  is  found  only  in  the  first  workings ; 
the  ore  in  depth  is  always  cinnabar.  At  the  Rattlesnake  mine  near 
Pine  Flat,  where  large  quantities  of  metallic  mercury  are  found,  the 
rock  contains  so  much  petroleum  that  it  has  been  necessary  to  make 
special  arrangements  to  burn  the  carbides  of  hydrogen,  since  the  dis- 
tillation of  the  petroleum  causes  an  extra  quantity  of  poor  soot  to 
be  formed  in  the  condensation-chambers.  At  the  Geysers  the  ore  is 
associated  with  large  quantities  of  sulphur  and  gypsum,  so  that  in 
a hand  specimen  there  is  often  more  sulphur  than  cinnabar,  which,  is 

2 


4 


NOTES  ON  THE  TREATMENT 


a serious  impediment  to  working,  especially  for  the  modern  style  of 
furnace  with  iron  condensers,  and  causes  so  much  soot  to  be  formed 
that  it  has  been  known  to  penetrate  as  far  as  the  blower,  and  to  so 
completely  clog  it  as  to  prevent  its  revolution. 

The  ore  coming  from  the  mine  is  more  or  less  hand-picked.  In 
one  or  two  cases  attempts  have  been  made  to  treat  the  poorest,  and 
especially  the  very  fine  ores,  mechanically  as  at  the  California  works. 
The  apparatus  used  for  the  purpose  is  very  rude,  and  the  treatment 
does  not  seem  to  be  very  successful,  as  there  is  visibly  a considerable 
loss  in  the  tailings.  7 

Usually  the  fine  ore  is  not  concentrated ; it  is  taken  as  it  comes 
from  the  mine,  mixed  with  dirt  and  made  up  into  adobes,  which 
have  no  regular  size  or  weight,  and  treated  in  the  furnace. 

The  processes  by  which  the  ore  is  treated  are,  first,  the  process  by 
precipitation ; second,  by  roasting.  The  precipitation  is  done  in 
retorts  with  lime,  and  consists  of  oxidizing  the  sulphur  by  means  of 
an  excess  of  air,  and  so  producing  sulphate  of  lime  and  free  mercury. 
The  roasting  is  done  either  in  retorts,  or  in  other  furnaces  which  are 
not  continuous,  and  in  several  styles  of  continuous  furnaces.  The 
reaction  consists  in  volatilizing  the  sulphur  and  oxidizing  it  so  as  to 
produce  free  mercury  and  sulphuric  acid,  which,  with  the  moisture 
of  the  fuel  and  ore  is  condensed  and  allowed  to  run  to  waste.  The 
furnaces  which  are  not  continuous  are  a modification  of  the  old  Idria 
furnace,  which  is  used  at  Knoxville  and  at  New  Almaden  in  South 
California.  Those  which  are  continuous  are  the  Luckhart,  which  is 
used  at  Sonoma,  and  which  was  being  built  at  the  Rattlesnake  mine 
and  elsewhere  ; and  the  Knox  furnace,  which  is  in  very  successful 
operation  at  the  Redington,  Manhattan,  and  the  California  mines, 
and  elsewhere.  There  are  a number  of  other  varieties  of  furnaces,  none 
of  which,  however,  I saw.  To  these  processes  should  be  added  the 
process  of  distillation,  if  the  metallic  mercury  of  the  outcrops  were 
found  in  sufficient  quantities  to  warrant  the  ore  being  treated  alone. 
This,  however,  has  never  been  the  case,  and  the  small  quantities  that 
are  found  are  charged  in  the  furnace  with  the  other  ores,  either  as 
rock  ore  or  as  adobes.  Very  little  effort  is  made  to  sort  the  ore,  and 
this  generally  consists  in  a rough  attempt  at  hand-picking.  No  as- 
says of  any  kind  are  made.  The  furnace  manager,  or  miner,  judges 
by  the  eye  that  the  ore  contains  one,  two,  three,  ten,  or  twenty-five 
per  cent.,  as  the  case  may  be,  and  hence  there  is  little  faith  to  be 
placed  in  the  statement  of  many  of  the  advocates  of  different  kinds 
of  furnaces,  that  their  furnace  yields  such  and  such  a percentage  of 
the  assay  value. 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


5 


The  mercury  produced  is  put  up  in  iron  flasks,  which  contain 
76J  lbs.  each,  with  an  iron  screw  for  a cork,  and  shipped.  Irregu- 
lar flasks,  as  they  are  called,  contain  less  or  more. 

METHOD  OF  DISTILLATION. 

AMERICAN  MINE. 

At  the  American  Mine,  near  Pine  Flat,  all  the  ore  is  crushed  fine 
in  an  ordinary  California  stamp-mill,  with  a battery  of  ten  stamps, 
which  is  run  at  a high  velocity.  It  is  then  mixed  with  lime,  and 
treated  in  retorts.  The  average  yield  of  the  ore  is  said  to  be  two 
per  cent. 

There  are  twelve  retorts  9 feet  long,  2 feet  wide,  and  18  inches 
high  in  the  middle.  They  are  made  of  cast  iron,  and  are  D-shaped 
like  the  ordinary  gas  retort,  and  are  arranged  in  benches  of  three, 
the  centre  one  being  the  highest,  so  that  there  are  four  fireplaces  to 
the  twelve  retorts.  The  charge  consists  of  150  lbs.  of  crushed  ore, 
to  which  ten  per  cent,  of  quicklime  is  added.  This  charge  is  intro- 
duced into  the  muffle  in  an  iron  spoon  6 feet  long,  9 inches  wide, 
and  6 inches  deep.  This  is  carried  by  three  men,  one  taking  the 
end,  which  has  an  iron  handle  2 feet  long,  with  a crossbar  of  wood 
of  the  same  length.  The  middle  is  supported  on  an  iron  bar,  curved 
in  the  middle  to  fit  the  shape  of  the  spoon,  with  handles  projecting 
18  inches  from  the  sides,  and  is  carried  by  two  men.  This  spoon  is 
introduced  into  the  muffle  and  shoved  to  its  end.  It  is  drawn  out 
by  short  jerks,  so  as  to  leave  the  charge  in  the  retort.  The  doors  of 
the  retort  are  then  fastened  by  means  of  thumb-screws,  and  luted 
with  wood  ashes,  and  fired  during  four  hours,  when  the  charge  is 
withdrawn.  Not  over  500  lbs.  per  retort  is  treated  in  twelve  hours. 

The  condensation  pipes  are  in  the  back  of  the  retort.  A pipe, 
about  18  inches  long,  connects  each  retort  with  a vertical  pipe  about 
5 feet  long,  which  connects  with  a horizontal  pipe  6 inches  in 
diameter,  placed  in  a water-tank  at  a lower  level  than  the  front  of 
the  furnace,  and  which  receives  the  pipes  of  all  the  retorts.  Every 
six  retorts  are  so  arranged  that  they  discharge  their  condensed  mer- 
cury through  a siphon  pipe. 

The  soot  is  treated  with  lime  as  is  usual. 

These  works  are  new  and  carefully  built.  It  is  surprising  to  see 
works  upon  which  no  expense  seems  to  have  been  spared,  apparently 
put  up  to  treat  such  very  small  quantities  at  a time  of  very  lean  ore 
by  such  a system  ; not  even  the  possible  economy  of  the  retort  sys- 
tem seems  to  have  been  taken  into  account.  There  did  not  seem  to 
be  sufficient  care  taken  with  the  condensation  apparatus,  for  the  air 


6 


NOTES  ON  THE  TREATMENT 


for  some  distance  from  the  works  was  filled  with  mercurial  vapors ; 
and  though  the  workmen  wore  wet  sponges  over  their  mouths  and 
noses,  most  of  them  were  more  or  less  salivated.  I did  not  visit  the 
mines;  but  any  mine  which  would  justify  such  carefully  erected 
works  with  stamp-mills,  would  certainly  justify  the  erection  of  other 
and  less  wasteful  furnaces. 

METHOD  OF  ROASTING. 

The  method  by  roasting  is  the  one  which  is  the  most  extensively 
used,  and  all  the  different  varieties,  of  furnaces  are  adapted  to  it. 
Those  most  in  use  are  retorts,  and  the  modified  Idria  furnace  of  the 
non-continuous  varieties,  the  Luckhart  and  the  Knox  furnace  of  the 
continuous  ones. 

NON-CONTINUOUS  FURNACES. 

Missouri  Mine. 

At  the  Missouri  mine,  near  Pine  Flat,  the  average  yield  of  the  ore 
is  from  one-half  to  2 per  cent,  of  mercury.  The  cinnabar  is  irregu- 
larly scattered  through  a chalcedony  found  in  very  irregular  masses 
in  serpentine ; the  large  pieces  are  crushed  in  a Blake’s  crusher  to 
about  1 cubic  inch  in  size.  There  are  two  benches  of  retorts,  one  con- 
taining two  retorts  and  holding  250  pounds  of  charge  at  a time,  and 
the  other  containing  three  retorts  and  holding  350  pounds,  so  that 
the  small  retorts  treat  1000  and  the  large  ones  2100  pounds  in 
twenty-four  hours.  The  large  retorts  have  been  in  use  but  a short 
time,  and  have  consequently  produced  but  little.  The  retorts  are 
D-shaped,  and  are  here  9 feet  long,  12  inches  high,  and  18  inches  wide 
on  the  bottom ; they  are  charged  every  twelve  hours  by  means  of  a 
shovel.  At  the  Lost  Ledge  mine  the  same  company  have  three 
retorts  which  are  only  five  feet  in  length,  and  have  a capacity  of  500 
pounds,  or  160  pounds  each ; they  are  charged  every  four  hours,  and 
consequently  treat  3000  pounds  of  ore  in  twenty-four  hours.  It 
takes  three-quarters  of  an  hour  at  the  Missouri  mine  to  discharge 
and  charge  the  large  retorts,  and  half  an  hour  for  the  small  ones, 
so  that,  as  there  is  not  much  difference  in  the  wear  and  tear,  the 
large  size  retorts  are  the  most  advantageous.  They  are  never  filled 
full,  as  there  would  be  danger  that  the  pressure  of  the  discharging 
vapors  might  force  an  exit  through  the  luted  joints. 

When  the  furnace  is  ready  to  be  discharged  the  men  cover  their 
mouths  and  noses  with  wet  sponges,  tied  on  with  bandages,  and  then 
remove  the  cover  of  the  retorts.  When  they  are  about  to  be  re- 
moved a little  fan  placed  on  the  condensing  pipes  is  set  in  motion  to 
cause  ah  aspiration  through  the  retorts,  so  that  no  mercurial  fumes 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


7 


escape.  When  the  fumes  cease  to  be  dense  the  charge  is  drawn  out 
of  the  retort  with  long  hoes  on  to  the  floor  in  front  of  the  furnace. 
The  discharged  ore  is  at  a cherry -red  heat,  and,  as  it  is  not  entirely 
free  from  mercury,  a considerable  quantity  of  fumes  are  given  off  so 
that  the  precaution  of  using  the  bandage  over  the  mouth  and  nose 
is  indispensable.  After  the  ore  has  all  been  raked  out,  it  is  carried 
as  quickly  as  possible  a short  distance  from  the  furnace  and  extin- 
guished with  water,  a new  charge  being  put  in  in  the  meantime. 
This  is  an  exceedingly  bad  system,  as  the  workmen  are  constantly 
exposed  to  fumes,  more  especially  when  water  is  scarce,  since  small 
quantities  at  a time  thrown  on  the  very  hot  ore  seems  to  increase  the 
quantity  of  fumes.  The  men,  however,  seem  to  know  this,  and 
take  the  necessary  precautions,  as  none  of  them  were  salivated.  The 
product  of  the  small  retorts  varies  from  3f  to  70  pounds  of  mercury 
in  twenty-four  hours.  The  large  ones  yield  from  10  to  100  pounds. 

As  the  two  benches  of  retorts  are  at  some  distance,  each  bench 
requires  one  man  per  shift  of  twelve  hours,  who  is  paid  $3.75  a 
day.  They  burn  3J  cords  of  wood  in  twenty-four  hours.  Wood  costs 
$6  per  cord,  and  labor  $64  per  month  with  board.  Each  retort  is 
connected  by  a short  joint,  with  a horizontal  pipe  leading  to  the 
condenser,  which  must  be  large  enough  to  insure  of  its  not  being 
clogged  by  the  soot.  This  pipe  is  of  cast  iron,  and  is  30  feet  long 
and  6 inches  in  diameter.  The  pipes  leading  from  the  retorts,  in 
the  latest  and  best  construction,  come  from  the  back,  where  there  is 
plenty  of*  room  and  they  are  not  in  the  way,  so  that  they  can  be 
large.  Formerly  they  were  made  to  come  from  the  front,  where 
they  were  in  the  way  of  the  workmen,  and  were  constantly  in  danger 
of  being  damaged  by  the  charge  lying  against  them  as  it  was  drawn 
from  the  furnace. 

The  condensing  apparatus  consists  of  two  cast-iron  boxes  3 feet  by 
2,  and  2 feet  high,  turned  down  into  cast-iron  tanks,  with  inclined  bot- 
toms, which  are  covered  with  water.  From  the  bottom  of  these  tanks 
a wrought-iron  pipe,  curved  in  the  shape  of  an  S,  is  placed,  with  the 
arms  sufficiently  long  to  counterbalance  the  pressure  of  the  water,  so 
that  the  mercury  flows  from  it  continuously.  The  mercury  commences 
to  flow  two  and  one-half  hours  after  the  charge  is  put  in.  Between 
the  two  cast-iron  boxes,  which  are  connected  with  each  other,  and  on 
the  main  pipe,  a small  fan-blower  is  placed,  and  is  made  to  suck  out 
the  vapors  from  the  retorts,  or  when  the  condenser  is  to  be  cleaned 
into  an  exterior  pipe.  The  fan  is  inclosed  in  a box  18  inches  square, 
into  which  there  is  an  opening  1 foot  in  diameter,  closed  with  a hy- 
draulic packing.  The  pipesand  condensers  are  cleaned  once  a week. 


8 


NOTES  ON  THE  TREATMENT 


In  the  small  furnace  140  pounds  of  soot  and  mercury  together 
are  collected ; this  is  put  into  a sheet-iron  pan,  8 feet  long,  3 feet 
wide,  6 inches  deep,  inclined  about  25°,  which  is  not  fixed,  but  is 
moved  from  place  to  place  as  convenience  may  require.  The  soot  is 
placed  at  its  upper  end,  and  is  worked  with  a hoe  for  a quarter  of  an 
hour,  to  separate  the  free  mercury.  Three  to  five  pounds  of  unslacked 
lime  without  water  are  then  stirred  into  it.  As  the  soot  is  already 
damp,  the  lime  soon  commences  to  slack ; it  is  left  until  it  slacks  en- 
tirely. No  one  goes  near  it  for  one-half  or  three-quarters  of  an  hour, 
on  account  of  the  vapors  arising  frdpi  it.  It  is  then  worked  with  a 
hoe  for  three  hours.  About  one  barrel  of  lime,  which  costs  $3  the 
barrel,  is  used  per  week  for  treating  the  soot.  The  mercury  as  it  is 
collected  runs  into  the  lower  part  of  the  pan,  and  is  taken  out  with 
a ladle  and  put  into  fiasks.  The  residue,  which  has  twice  the  bulk 
which  the  soot  originally  had,  is  added  to  the  next  charge  of  the 
retorts,  in  addition  to  the  charge  of  ore.  Such  a charge  will  produce 
about  10  pounds  more  of  mercury  than  usual.  From  140  pounds  of 
soot,  120  pounds  of  mercury  are  obtained  directly,  and  about  10 
pounds  more  from  soot  charged  in  the  furnace.  The  large  furnaces 
were  run  10  days;  200  pounds  were  taken  from  the  first  condensers 
and  pipes,  and  from  12  to  14  out  of  the  second  condenser.  When 
there  is  only  a small  amount  of  soot  to  be  treated,  a small  cast-iron 
sink  3 feet  by  18  inches  is  used,  the  drain-hole  being  placed  over  an 
enamelled  iron  vessel  1 foot  in  diameter,  and  6 inches  deep.  This 
vessel  is  used  because  ordinary  kitchen  utensils  answer  perfectly  well, 
and  can  be  had  much  cheaper  than  special  apparatus,  which  would 
work  no  better. 

The  expenses  are  for  twenty-four  hours  : 


2 men  at  the  retorts, $6.50 

3|-  cords  of  wood,  at  $6, 21  00 

Lime  for  soot,  .........  50 

Crushing  the  ore  two  days,  at  $1.25, 2.50 


There  does  not  seem  to  be  any  real  economy  in  using  this  retort 
system.  The  yield  is  not  greater,  nor  is  the  cost  of  repairs  and  run- 
ning less,  while  the  risk  of  salivation  is  greater.  There  is  certainly 
an  economy  of  first  installation,  and  this  seems  to  be  the  only  reason 
why  such  furnaces  are  used.  With  the  high  prices  of  quicksilver 
w’hich  have  ruled  during  1873  and  most  of  1874,  every  place  where 
ores  could  be  found  has  been  worked,  and  as  all  the  deposits  are 
irregular  and  uncertain,  the  owners  of  such  mines  have  not  felt 
themselves  justified  in  going  to  any  greater  expense.  I saw  no  well- 
developed  property,  nor  any  property  which  appeared  to  have  any 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


9 


future,  which  was  worked  with  retorts,  except  in  a few  instances, 
where  the  retorts  were  put  up  to  have  a yield  while  other  furnaces 
were  being  erected  on  the  property  developed,  or  where  the  mines 
were  evidently  being  worked  w7ith  too  small  a capital. 

MODIFIED  IDRIA  FURNACE. 

Redington  Works. 

As  an  example  of  non-continuous  working  with  shaft  furnaces,  I 
have  selected  the  practice  of  the  Redington  mine,  with  the  old  Idria 
furnace,  which  is  by  far  the  largest  mercury  works  in  North  California. 
But  as  everything  relating  to  this  variety  of  furnace,  which  is  destined 
in  a few  years  to  disappear  altogether,  is  of  interest,  I have  added 
some  details  relating  to  the  New  Almaden  furnace  of  the  same  type, 
which  I visited  shortly  after,  although  they  are  south  of  San  Fran- 
cisco. Great  attention  is  being  paid  to  the  question  of  condensation, 
which  is,  perhaps,  even  more  important  than  that  of  the  furnace. 
The  two  questions  are,  however,  intimately  connected,  and  are  en- 
gaging the  most  serious  study  of  all  persons  interested  in  the  metal- 
lurgy of  mercury. 

At  Knoxville,  the  Redington  Quicksilver  Company  treat  the  ores 
from  the  Redington  mine,  which  they  own,  in  both  the  modified 
Idria  furnaces,  of  which  they  have  two,  and  also  in  the  Knox  fur- 
naces, of  which  there  are  two  working,  and  two  in  the  course  of 
construction ; besides  these,  two  others  are  to  be  built.  The  furnaces 
are  situated  at  the  mines  and  within  a few  feet  of  the  ore  shaft.  The 
mine  produces  700  to  800  tons  of  cinnabar  per  week.  The  ore  occurs 
in  a sand-rock,  in  serpentine.  Much  pure  cinnabar  is  found,  and  a 
considerable  quantity  of  high  grade  ore,  but  the  average  yield  of  the 
whole  mine  is  about  3 per  cent.  Metacinnabarite  is  found  in  con- 
siderable quantities  in  these  mines.  Epsomite,  resulting  from  the 
decomposition  of  the  serpentine,  also  occurs  here  in  very  large  quan- 
tities, in  acicular  crystals  over  a foot  long.  The  ore  is  largely  asso- 
ciated with  pyrites.  About  one-tenth  of  the  ore  comes  from  the 
open  cut  made  in  the  side  of  the  hill.  From  the  mine  the  ore  is 
thrown  upon  screens  placed  one  over  the  other ; the  upper  screen  is 
made  of  round  iron  bars  1 \ inches  in  diameter,  placed  2 inches  apart 
at  the  top,  and  2J-  at  the  bottom.  The  screen  itself  is  5 feet  wide 
at  the  top,  5 feet  6 inches  at  the  bottom,  and  is  8 feet  long.  Whatever 
passes  over  this  screen  only,  is  hand-picked.  What  passes  through 
falls  upon  strong  iron-wire  screen  of  J-inch  mesh.  What  goes  over 
the  second  screen  goes  directly  to  the  furnace,  and  is  charged  with 
the  hand-picked  ore ; what  passes  through  is  treated  as  fine  ore ; all 


10 


NOTES  ON  THE  TREATMENT 


the  large  pieces  are  broken  by  hand.  Before  the  Knox  furnace  was 
introduced,  the  ore  was  dressed  by  hand  up  to  5 per  cent. 

All  the  fine  ore  is  mixed  with  dirt  and  made  into  adobes,  which 
are  sun-dried  and  stored,  for  use  in  the  modified  Idria  furnaces  ex- 
clusively. There  is  no  generally  adopted  size  for  the  adobes.  They 
are  made  in  roughly  constructed  wooden  frames,  made  by  the  work- 
men, which  wear  out  rapidly.  The  usual  sizes  are  9x4x4  inches. 
When  dry  such  adobes  weigh  12  pounds.  They  are  sometimes 
made  12  x 5 X 5 inches,  which  is  <a  very  large  size.  Such  adobes 
weigh  18  pounds.  The  smaller  siz6  is  the  one  most  generally  used. 
Seven  men,  at  $2  per  day,  can  make  6000  adobes.  Each  man  can 
mould  one  thousand,  but  the  six  men  require  one  man  to  loosen  and 
moisten  the  dirt,  and  to  mix  the  ore  with  it.  Making  the  adobes 
costs,  therefore,  $2.33  the  thousand.  The  cost  of  the  adobes  deliv- 
ered at  the  furnace,  ready  for  charging,  including  making,  carting, 
and  storing,  is  $5  the  thousand. 

The  modified  Idria  furnaces  (Plate  VIII,  Fig.  1)  are  built  one  on 
each  side  of  the  condensers,  which  are  at  right  angles  to  them.  Each 
of  these  furnaces  is  capable  of  treating  100  tons  of  ore  with  4000  to 
5000  adobes  per  week.  They  are  built  of  a porous  sandstone,  which 
is  found  a short  distance  from  the  works.  Each  furnace  has  a double 
fireplace,  B,  20  inches  in  width,  17  feet  long,  and  15  feet  high,  from 
the  spring  of  the  arch  of  the  fireplace.  The  total  inside  height  of  the 
fireplace  compartment  is  20  feet.  It  has  on  the  ore-chamber  side  a 
brick  screen  pierced  with  fourteen  openings,  the  size  of  one  brick,  and 
two  bricks  apart,  across  the  furnace,  and  fourteen  openings  in  height, 
also  two  bricks  apart.  ' The  fireplace  wall  has  been  repaired  once  in 
seven  years.  It  is  made  of  red  brick,  and  is  glazed  by  the  heat. 
The  ore  chamber,  C,  is  13  feet  by  10,  and  20  feet  high.  Its  walls  are 
4 feet  thick.  There  are  two  ore  discharge  openings,  32  by  20  inches, 
on  each  side,  at  the  bottom,  which  are  four  feet  above  the  ground. 
The  car  for  discharging  the  furnace  runs  under  a swinging  apron  of 
cast  iron,  and  the  ore  which  has  been  treated  is  raked  out  over  it. 
The  fireplace  and  condenser  wall  are  each  mere  screens  of  brickwork 
filled  with  holes,  which  are  the  starting-points  of  the  flues,  made  in 
the  charge.  As  the  condenser  side  is  constantly  exposed  to  the  acid 
vapors,  it  is  the  one  most  rapidly  worn.  It  has  been  renewed  twice 
in  five  years.  It  is  now  strengthened  with  an  abutment.  From 
constant  use  the  inside  walls  round  the  ore-chamber  have  become 
worn  away,  making  its  present  size  somewhat  larger  than  it  origi- 
nally was.  Beyond  the  ore-chamber  each  furnace  has  two  sandstone 
condensers,  D,  which  are  4 feet  wide,  13  feet  long,  and  20  feet  high, 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


11 


in  which  very  little  material  ever  collects,  never  more  than  two  flasks 
of  mercury  a week. 

In  the  drawing,  Fig.  1,  Plate  VIII,  these  furnace  condensers  are 
connected  with  the  main  condensing  chambers,  A,  by  the  flues,  E, 
which  are  supported  upon  arches,  and  which  enter  the  top  of  the 
first  chamber  of  the  main  condenser,  A.  The  length  of  the  flue 
between  the  furnace  and  the  main  condenser  is  8 feet,  and  the  fur- 
naces are  so  arranged  that  each  one  may  work  independently  into 
the  condenser,  the  connection  being  cut  off  at  will.  The  total  length 
of  each  furnace,  including  the  fireplace,  ore-chamber,  and  two  con- 
densing chambers,  is  36  feet,  its  total  width  is  17  feet,  total  outside 
height  24  feet.  The  main  condensers,  A,  consist  of  a series  of  twelve 
chambers,  each  of  which  is  4 feet  wide,  20  feet  long,  and  20  feet 
high  on  the  inside,  contained  in  a structure  at  right  angles  to  the 
furnaces,  and  which  is  common  to  both  of  them.  Each  one  of  these 
compartments  has  an  iron  door  on  each  side  on  a level  with  the 
bottom  of  the  chamber.  The  inside  walls  of  the  condensers  are  1 
foot  thick,  the  outside  18  inches.  They  are  braced  on  the  outside 
with  wooden  beams  8 x 10  inches,  which  are  tied  with  f-inches  round 
iron  rods.  These  rods  must  be  carefully  watched,  as  they  are  likely 
to  become  corroded  through,  and  allow  the  wall  to  fall,  and  thereby 
cause  serious  accident. 

The  walls  of  these  chambers  are  soon  saturated  with  mercury,  and 
become  soft  from  the  effects  of  the  acid  vapors.  The  stones  are  found 
corroded  for  a depth  of  6 inches,  and  some  of  the  interior  walls  have 
been  corroded  entirely  through.  Whenever  they  have  been  repaired 
with  brick,  it  is  found  to  be  quite  hard  and  to  resist  much  better 
than  the  stone. 

The  relation  of  the  condensing  surface  of  the  condensers  to  that  of 
the  charging  compartment  is  much  too  small.  The  relation  of  the 
condensing  volume  to  the  volume  of  the  furnace  should  be  at  least  as 
24  to  1.  In  this  furnace,  however,  it  is  not  more  than  one-half  of 
that  amount.  This  would  make  the  chambers  only  large  enough 
for  one  furnace.  That  the  condensing  capacity  is  not  sufficient,  is 
evident,  from  the  fact  that  metallic  mercury  has  supersaturated  the 
stones,  and  still  exudes  in  globules  from  the  walls  even  after  re- 
peated cleaning. 

The  flue  leading  to  the  chimney  is  also  built  of  cut  stone,  and  is 
250  feet  long.  It  is  oval,  4 feet  in  the  highest  diameter  inside, 
with  walls  2 feet  thick.  It  lies  against  the  side  hill.  The  chimney 
is  built  of  stone,  with  walls  3 feet  thick.  It  is  conical,  5 feet  in 
diameter  at  the  base,  and  50  feet  high. 


wWERSuurm;y 


of  HUNOlS 


12 


NOTES  ON  THE  TREATMENT 


The  furnace  is  charged  by  a windlass  from  above.  The  ore  is  let 
down  in  iron  buckets  3 feet  in  diameter,  and  30  inches  high.  The 
adobes  are  let  down  in  iron  cages  that  hold  150  adobes,  which  weigh 
about  a ton.  This  cage  is  3 feet  by  30  inches,  and  2J  feet  high. 
The  charging  compartment  is  ‘lined  with  adobes  2 to  5 thick,  piled 
close,  but  not  crowded.  Inside  of  this  the  ore  is  placed  in  pieces 
from  about  the  size  of  an  egg  to  twice  the  size  of  the  fist,  in  layers 
of  four,  18  to  24  inches  in  thickness,  then  four  to  five  channels  the 
size  of  an  adobe  are  built  of  adobes  over  the  ore.  Their  number  de- 
pends on  the  size  of  the  ore,  five  for  fine  ore,  and  four  for  coarse. 
These  channels  start  in  the  opening  of  the  fireplace  screen,  and  end 
in  the  opening  towards  the  condensation-chamber.  They  answer  the 
purpose  of  flues,  and  are  necessary  not  only  to  provide  a draft  and 
to  allow  of  the  heat  coming  in  contact  with  the  ore,  but  also  to  pre- 
vent the  charge  from  packing  together.  The  poor  soot,  or  that 
which  has  been  worked,  is  charged  on  top  of  every  layer  of  ore.  A 
new'  layer  of  ore  is  then  put  in,  and  so  on,  until  the  chamber  is 
nearly  full.  A layer  of  fine  ore  and  poor  soot  is  placed  near  the  top, 
and  this  is  covered  over  with  clay  and  straw.  The  compartments 
are  closed  with  cast-iron  pans,  which  are  filled  with  water,  the  joints 
between  the  pans  and  against  the  masonry  being  made  tight  with 
ashes  or  cement.  These  pans  are  10J  feet  long,  4J  feet  wide,  5 inches 
deep.  The  cold  water  flows  constantly  from  an  inch  pipe  into  the 
pan  nearest  the  fireplace.  A spout  from  every  pan  carries  the  water 
to  the  next  pan,  so  that  they  are  always  full.  Each  pan  is  provided 
with  two  eyes  at  the  sides  for  their  removal  when  it  is  necessary  to 
recharge  the  furnace.  One  furnace  is  charged  on  Monday,  and  is 
fired  Monday  night,  and  is  kept  burning  until  Thursday  morning. 
During  this  time  two  cords  of  wood  are  burned  to  each  furnace. 
The  sulphur,  to  a great  extent,  answers  for  fuel,  for  there  is  always 
an  excess  of  sulphur  in  the  shape  of  pyrites  in  the  ore.  The  other  fur- 
nace is  charged  on  Tuesday,  and  is  fired  Tuesday  evening,  and  kept 
burning  until  Friday.  One  furnace  will  thus  be  cooling  on  Satur- 
day and  Sunday,  and  the  other  on  Sunday  and  Monday.  A little 
mercury  commences  to  run  in  D on  Tuesday,  and  in  the  1st,  2d,  and 
3d  compartments  of  the  main  condenser.  It  runs  most  freely  Wed- 
nesday and  Thursday.  By  Thursday  the  mercury  condenses  quite 
in  the  end  of  the  condenser,  but  only  in  very  small  quantities;  150, 
sometimes  200,  flasks  are  collected  from  both  furnaces  during  the 
week;  most  of  it  comes  from  the  5th  and  6th  condensers.  On  Wed- 
nesday it  commences  in  the  5th  and  6th,  and  runs  from  here  con- 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


13 


tinually  until  the  furnace  is  discharged.  The  most  of  the  mercury 
is  obtained  when  the  furnace  is  cooling  down.  When  the  draft  is 
good  and  the  ore  moderately  rich  the  yield  will  not  be  less  than  200 
flasks  a week. 

The  bottoms  of  the  condensing-chambers  were  originally  built  in- 
clined toward  the  centre,  as  is  shown  in  the  lower  part,  Fig.  2,  with 
the  intention  of  having  all  the  mercury  in  all  the  condensers  run 
out  through  a common  opening  made  for  the  purpose,  but  the  open- 
ings in  the  partition  walls  of  the  condensing-chambers  very  soon 
became  clogged,  and  so  much  mercury  was  absorbed  in  the  masonry 
that  this  was  shortly  abandoned.  The  present  disposition  is  iron 
pans  sloping  from  the  centre  toward  the  outside,  as  is  shown  in  the 
upper  part,  Fig.  2,  which  are  placed  3 feet  above  the  furnace  bottom 
of  the  old  construction,  which  has  not  been  altered,  so  that  there  is 
a space  of  considerable  size  under  the  bottom  of  the  pans.  The  pans 
are  made  in  three  pieces,  which  overlap  each  other.  This  is  espe- 
cially necessary,  as  when  the  walls  get  old  and  fall,  the  whole  pan 
would  then  be  liable  to  be  broken.  Tiles  placed  upon  the  top  of  the 
pans  to  protect  them  have  been  used  with  good  effect.  The  castings 
with  this  protection  have  lasted  already  four  years,  and  are  seemingly 
perfect.  The  cast  iron  without  the  tiles  lasts  only  two  years,  at 
which  time  it  is  corroded  by  the  sulphuric  acid  which  condenses 
from  the  furnace. 

On  Saturday  the  iron  doors  at  the  bottom  of  the  condensation- 
chambers  are  taken  off,  and  a workman  with  a long  hoe  collects  the 
soot  on  the  pan  and  that  from  the  walls  about  two  feet  above  the 
bottom  of  the  pan ; what  is  higher  up  on  the  wall  is  left  to  collect 
there  until  it  falls  of  its  own  weight.  75  to  100  bushels  of  soot  are 
collected  in  buckets  every  week  from  the  bottom  of  the  condensing- 
chambers,  which  yields  from  5 to  20  flasks  of  mercury.  This  soot 
is  a mechanical  mixture  composed  of  ordinary  soot  condensed  from 
the  smoke  of  the  fuel,  ashes,  fine  dust  and  dirt  carried  over  from  the 
ore,  volatilized  cinnabar,  and  sublimated  mercury  in  very  fine  glob- 
ules. It  is  usually  taken  from  the  condenser  damp,  owing  to  the 
condensation  of  steam  from  the  moisture  in  the  fuel  and  ore,  and  the 
acid  vapors.  This  soot  is  removed  in  buckets,  14  inches  in  diameter 
at  the  bottom,  30  at  the  top,  and  33  inches  high.  Two  such 
buckets  filled  one  foot  high  are  taken  from  each  side  of  the  conden- 
ser. Sometimes  as  many  as  eight,  and  sometimes  not  as  many  are 
taken.  It  takes  two  men  two  days  to  clean  out  and  work  the  soot 
from  all  the  five  condensers  in  an  ordinary  working  of  the  furnace. 
The  amount  collected  is  very  variable.  When,  for  any  reason,  such 


14 


NOTES  ON  THE  TREATMENT 


as  a stoppage  for  repairs,  the  furnace  cools,  a large  quantity  of  soot 
becomes  detached  at  the  time  the  furnace  is  lit.  The  amount  of 
mercury  collected  from  the  soot  varies  from  5 to  20  flasks  a week. 
The  flue  leading  to  the  chimney  is  cleaned  once  in  two  or  three  weeks ; 
about  one  bushel  of  soot  is  taken  from  it.  This  is  not  kept  sepa- 
rate, but  is  mixed  with  that  taken  from  the  condensers. 

It  takes  ten  men  one  day  to  charge  each  furnace,  and  six  men  one 
day  to  discharge  it.  The  six  men  are  paid  about  $35  per  month  and 
board,  making  about  $1.90  a dayy  There  is  a fireman  and  one  man 
to  clean  and  repair  the  flasks  and  to  fill  them.  They  work  during 
the  day  only.  Each  shift  of  twelve  hours  has  its  own  foreman. 
This  does  not  include  the  men  working  up  the  soot.  When  the 
draft  is  not  good  a fire  is  placed  at  the  foot  of  the  chimney,  which 
is  fifty  feet  high,  to  increase  the  draft.  The  draft  depends  for  the 
most  part  upon  the  way  the  furnace  has  been  charged,  but  is  some- 
times due  to  the  direction  of  the  wind.  This  draft  furnace  is  oftenes.t 
used  when  the  furnace  has  been  allowed  to  get  cool.  Not  a cord  of 
wood  per  month  is  required  for  this  purpose.  In  winter,  fall,  and 
spring  there  is  no  trace  of  mercury  in  the  flue,  but  when  the  weather 
is  hot  it  collects  inside,  near  the  top  of  the  chimney,  which  is  pro- 
vided with  a ladder  in  order  to  make  any  observations  on  the  escape 
of  gases  at  the  top  which  may  be  desirable.  When  the  furnace  is 
out  of  repair  in  very  hot  summer  weather,  it  is  apparent  that  some 
mercury  escapes.  The  joints  of  the  furnace  are  made  so  tight  that  no 
accident  arises  from  salivation  except  through  the  carelessness  of  the 
men.  As  soon  as  the  workmen  experience  any  sensitiveness  about 
the  mouth  they  are  instructed  to  go  to  the  office,  and  are  there  fur- 
nished with  a mouth- wash,  consisting  of  2 parts  of  cinchona,  1 part 
tincture  of  myrrh,  and  3 parts  water,  but  no  case  of  real  salivation 
except  from  the  carelessness  of  the  men,  has  occurred  in  a great 
many  years. 

Twice  in  a year  a general  clean-up  is  made.  This  is  done  by 
putting  iron  pipes,  24  inches  in  diameter,  in  compartment  D,  and 
three  in  the  flues  leading  to  the  chimneys,  both  to  hasten  the  cool- 
ing and  ventilate  them  while  they  are  being  cleaned.  The  walls  of 
the  condensers  are  cleaned  by  scraping.  On  account  of  the  dust 
arising  from  the  falling  soot,  it  is  necessary,  when  this  work  is  done, 
for  the  men  to  wear  a wet  sponge  over  the  mouth  and  nose,  which  is 
covered  with  a thin  cloth  tied  behind  the  head.  At  this  work,  the 
men  relieve  each  other  every  fifteen  minutes.  After  scraping,  the 
walls  are  thoroughly  washed.  It  takes  eight  men  two  days  to  scrape 
and  wash  the  walls,  flues  and  condensers.  The  soot  so  detached 


OF  MERCURY  IN  NORTH  CALIFORNIA.  15 

contains  a large  amount  of  mercury.  From  such  a general  clean-up 
as  many  as  one  hundred  flasks  have  been  collected.  The  soot  in  the 
first  condenser  is  often  6 inches  thick  in  concretions.  It  is  here  hard 
and  solid,  but  in  the  other  condensers  it  is  soft  and  light.  The  light 
soot  upon  the  walls  is  of  very  variable  thickness,  but  is  rarely  less 
than  1 to  2 inches  thick.  It  sometimes  reaches  as  high  as  6 
inches  after  a long  run  without  cleaning.  When  there  is  very  rich 
soot  it  may  often  be  as  thick  as  6 inches  on  the  bottom  of  the  iron 
pan.  The  soot  is  richest  in  the  fourth,  fifth,  and  sixth  condensers, 
but  it  is  always  very  unevenly  distributed.  In  all  the  compart- 
ments in  the  space  below  the  iron  pans  a hard  concrete,  consisting 
of  hardened  soot  and  mercury  in  globules,  is  found. 

The  furnaces  with  the  condensers  cost  originally  between  $100,000 
and  $125,000;  they  have  been  built  eight  years,  and  have  been  re- 
paired three  times,  parts  of  six  partition  walls  having  falling  down 
at  the  flue  end.  At  the  furnace  end  the  wall  is  good.  The  walls 
after  having  been  scraped  and  washed  every  day  for  a month  still 
showed  mercury  in  globules  all  over  them,  a few  hours  after  they 
became  exposed  to  the  heat  of  the  sun.  All  the  stone  taken  out  of 
the  condensation-chambers  during  repairs  is  carefully  preserved  and 
is  treated  as  very  rich  ore. 

The  first  time  that  the  furnace  was  charged  the  ore  was  picked. 
At  the  top  of  the  charge,  over  the  rich  ore,  6 to  7 feet  of  rich  soot 
were  put  in,  but  the  heat  did  not  reach  it.  The  charge  being  un- 
usually rich,  should  have  yielded  five  hundred  flasks  of  mercury, 
but  all  but  nine  flasks  of  it  were  absorbed  by  the  walls. 

This  furnace  has  been  definitely  abandoned  at  Knoxville.  The 
masonry  has  been  altered  into  Livermore’s  inclined  continuous  fur- 
nace, which  is  adapted  to  treat  fine  ores,  and  since  its  introduction, 
in  the  earlier  part  of  1875,  no  adobes  are  made.  The  cost  of  alter- 
ing the  furnace  was  only  $1200. 

Average  cost  per  week  of  reducing  1 ton  of  ore  in  the  modified 
Idria  furnace,  at  the  Redington  mine,  furnaces  Nos.  1 and  2,  in  1874: 


5£  cords  of  wood  at  $5, $27.50 

36  days,  furnaceman,#fireman  and  his  assistant,  . . . 86.00 

20  days,  laborers  charging  furnace,  . . . . .38.60 

12  days,  laborers  discharging  furnace,  .....  23.15 

8 days,  laborers  working  soot, 14.55 

8 days,  fireman,  . . . . . . . . .14.55 

9000  adobes  at  $5  per  thousand, 45.00 


Total  charge  of  200  tons  cost,  ....  $249.35 

Average  cost  per  ton  for  reduction,  ....  $1.25 


16 


NOTES  ON  THE  TREATMENT 


New  Almaden  Works. 

At  New  Almaden,  the  Quicksilver  Mining  Company  have  six 
furnaces  of  the  modified  Idria  type,  built  of  brick,  which  produced 
in  the  year  1874, 11,042  flasks  of  76  J pounds  each,  or  920  flasks  per 
month.  Four  of  these  have  a capacity  of  50  tons,  one  a capacity 
of  70,  and  one  100  tons  of  ore  a week.  They  run  a week,  so  that 
each  furnace  makes  four  charges  a month.  Each  furnace  has  from 
sixteen  to  twenty-two  brick  cond^nsing-chambers,  the  numbers  vary- 
ing with  its  ore  capacity.  The  bottom  of  the  chambers  inclines  from 
the  centre  toward  the  doors.  The  floor  is  built  of  brick,  and  is 
covered  with  cement.  Beside  the  brick  condensers,  each  furnace  has 
four  to  five  wooden  condensers,  which  are  26  feet  long,  14  feet  wide, 
20  feet  high,  divided  into  six  compartments  of  equal  size.  As  the 
result  of  the  addition  of  these  wooden  chambers,  one  of  the  flues, 
which  formerly  yielded  in  the  general  clean-up  from  60  to  100  flasks 
of  mercury,  yielded  in  the  year  1873  only  two  flasks,  and  the  largest 
part  of  this  was  found  near  the  outlet  from  the  condensers,  and  no 
signs  of  metal  were  found  further  on. 

It  is  the  present  intention  to  cut  up  the  blocks  of  brick  condensers 
by  taking  down  the  outside  wall  of  one  or  more  compartments,  and 
making  the  dividing  walls  the  exterior  walls  of  the  new  structure. 
The  former  condensers  will  thus  be  divided  into  three  or  more 
separate  buildings.  A much  larger  radiating  surface  being  exposed 
in  this  way,  it  is  expected  that  the  condensation  will  be  much  more 
perfect.  Adobes  10  x 4\  x 4J  inches  in  size,  made  of  the  fine  ore 
mixed  with  dirt,  are  placed  over  the  floor  of  the  ore-chamber,  one 
adobe  thick  the  entire  height  of  the  sides ; ore  is  then  put  2J  to  3 feet 
in  thickness,  then  a layer  of  adobes,  in  which  five  flues  from  one  side 
to  the  other  of  the  furnace  are  made,  and  then  ore,  and  so  on  to  the 
top.  The  top  is  covered  with  a layer  of  adobes,  and  then  a layer  of 
straw  2 or  3 inches  thick,  and  then  ordinary  clay  and  mud,  to  make 
it  even  with  the  top,  and  over  this  ashes.  Any  cracks  that  may 
occur  are  filled  in  with  ashes.  When  the  furnace  is  filled,  one-third 
of  the  charge  will  be  adobes ; sometimes  the  furnace  is  run  on  adobes 
alone.  It  takes  six  men  one  day  to  charg&  the  jiirnace.  It  takes 
one  man  part  of  twelve  hours  to  keep  up  the  fire.  It  takes  four 
men  one  day  to  discharge  it.  The  charging  is  done  by  the  company, 
as  it  must  be  carefully  done,  but  the  discharging,  as  it  requires  no 
supervision,  is  done  by  contract.  The  fire  is  kept  up  for  ninety -six 
hours,  and  during  this  time  18  cords  of  wood  are  burned  for  100 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


17 


tons  of  ore.  The  wood  costs  from  four  to  six  dollars  a cord.  The 
ore  is  discharged  twelve  hours  after  the  fire  is  drawn ; twenty-four 
hours  afterwards  the  soot  is  taken  out. 

The  mercury  commences  to  condense  fourteen  to  sixteen  hours 
after  the  furnace  is  lit.  If  the  ore  is  very  rich  it  sometimes  com- 
mences to  condense  in  eight  hours.  It  appears  first  in  condenser 
No.  1.  In  Nos.  1,  2,  3,  4,  and  5,  it  runs  for  ten  hours;  after  this 
it  runs  in  Nos.  3,  4,  5,  6,  7.  It  appears  in  No.  7 on  the  second 
day,  after  which  it  ceases  to  run  in  the  first  four  condensers,  but  con- 
tinues to  run  in  all  the  others.  The  greater  part  collects  in  Nos.  9, 
10,  and  11.  Before  the  fire  is  drawn,  half  of  all  the  mercury  is  con- 
densed, which  is  in  about  forty  hours,  gradually  diminishing  until 
it  ceases  to  condense.  A small  amount  of  mercury  still  runs,  how- 
ever, the  flow  being  kept  up  by  the  dripping  from  the  walls.  From 
the  bottom  of  each  of  the  condensers  there  are  small  pipes  leading 
into  an  outside  trough,  to  allow  any  mercury  that  forms  to  run  im- 
mediately into  the  gutter,  from  which  it  is  discharged  into  the  recep- 
tion basin. 

The  iron  doors  which  close  the  entrance  to  the  brick  condensers 
have  been  given  up,  except  for  the  first  four  or  five  chambers,  and 
are  now  replaced  by  ordinary  glass  window-frames  3x3  feet,  with 
six  panes  of  glass.  It  is  found  that  there  is  a material  difference  in 
the  condensation  since  they  have  been  adopted.  The  condensers 
made  of  wood  and  glass,  which  were  patented  in  May,  1874,  are 
in  successful  operation  here.  They  are  certainly  much  cheaper, 
and  it  would  seem  a much  better  condenser,  and  less  likely  to  get 
out  of  repair  than  the  iron  ones  used  elsewhere.  This  kind  of  con- 
denser requires  no  water,  and  is,  therefore,  applicable  everywhere. 
The  want  of  water  in  many  places  in  California  is  often  a serious 
drawback  to  the  working  of  the  ores.  Four  such  condensers  are  at 
work  at  New  Almaden.  Each  one  has  a volume  of  2640  cubic 
feet,  and  1196  square  feet  of  condensing  surface,  or  altogether 
10,560  cubic  feet  volume,  and  4784  square  feet  of  surface.  They 
have  cost  only  $1500,  which  is  the  smallest  cost  for  any  such 
amount  of  condensing  surface  known.  If  they  work  as  well  as  they 
promise  they  will  replace  at  least  half  of  the  iron  or  brick  con- 
densers. 

The  soot  is  collected  in  the  same  way  as  at  Knoxville.  That  col- 
lected from  four  charges  gave  18  flasks  of  mercury.  The  same  four 
charges  produced  474  flasks.  The  soot  condenses  in  all  the  con- 
densers from  No.  4 on;  the  most  of  it  collects  in  10,  12,  and  14,  or 
about  in  the  middle.  On  an  average  about  a lime-barrelful  per 


18 


NOTES  ON  THE  TREATMENT 


week  is  collected  from  each  condenser.  One  man  does  the  whole 
cleaning  np. 

The  soot  was  formerly  placed  on  an  inclined  plane,  and  stirred 
and  slightly  rubbed  with  a wooden  hoe.  A certain  quantity  of 
quicksilver  separated  and  ran  out  into  a vessel  prepared  for  it,  but 
left  a very  large  quantity  still  remaining  in  the  soot,  which  was 
afterwards  treated  with  lime.  This  method,  which  is  in  general  use 
and  takes  a great  deal  of  time,<^has  been  given  up  here.  The  soot 
is  now  put  into  a hemispherical  boiler  about  3 feet  in  diameter; 
it  is  mixed  with  boiling  water  from  a vertical  boiler,  used  for  this 
purpose  only.  About  half  of  the  bulk  of  soot  is  added  in  wood- 
ashes,  and  the  whole  thoroughly  stirred  with  an  iron  hoe  for  three- 
quarters  of  an  hour,  when  the  separation  is  complete.  It  is  then 
allowed  to  remain  an  hour  and  settle,  and  during  this  time  another 
boiler  is  worked.  The  mercury  collects  in  the  bottom  of  the  vessel, 
and  flows  out  of  a siphon -shaped  pipe,  so  that  only  the  pure  mer- 
cury is  discharged.  The  water  is  drawn  off  afterwards,  and  the 
soot  remaining  behind  is  thrown  into  a heap,  and  when  dry  is  placed 
upon  the  top  of  the  furnace  near  the  flue  where  the  flame  passes,  as 
it  still  contains  some  sulphur.  It  is  claimed  that  all  the  mercury  in 
the  soot  is  separated  in  this  way  and  with  much  less  labor  than  by 
the  former  method.  This  process  was  patented  October  4th,  1873. 

It  takes  one  man,  working  ten  hours,  four  to  five  days  to  work 
the  soot  of  six  furnaces. 

The  fuel  used  here  is  wood,  or  ordinary  charcoal  made  from  oak, 
or  a mixture  of  charcoal  and  coke.  It  requires  75  lbs.  of  coke  and 
charcoal  mixed  to  3000  lbs.  of  ore  and  adobes,  or  equal  quantities 
in  bulk. 

This  furnace,  as  used  here  and  at  Knoxville,  must  be  considered 
as  a very  great  improvement  on  the  old  Idria  furnaces,  as  there  are 
no  arches  in  the  ore-chamber  which  are  likely  to  break  down  with- 
out warning. 

The  method  of  charging  large  and  small  ores  and  arranging  air- 
channels  by  means  of  adobes  prevents  the  charge  from  packing,  and 
gives  all  the  space  which  is  required  for  the  circulation  of  the  air 
and  heat,  and  allows  of  using  a poorer  ore  than  could  be  otherwise 
used.  The  labor  of  making  the  adobes,  which  is,  however,  only 
$5  the  thousand,  must  be  regarded  as  a necessary  expense,  as  the 
furnace  could  not  be  run  without  them ; as  the  expense  of  making 
the  air-channels  of  large  pieces  of  ore  would  be  too  great,  and  there 
would  be  no  certainty  that  they  would  last  if  so  made.  The  adobes, 
however,  do  not  change  their  form,  and  the  air-channels  once  made 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


19 


remain  as  they  were  made  in  the  charge.  The  making  of.  adobes  is, 
however,  one  of  the  expenses  to  be  avoided  in  the  furnace  of  the 
future,  and  the  most  careful  attention  now  being  given  to  the  con- 
struction of  furnaces  which  will  allow  of  the  fine  ore  being  treated 
as  it  comes  from  the  screens.  Although  this  furnace,  with  its  ex- 
pensive, cumbersome  method  of  condensation,  is  ,a  great  improve- 
ment on  the  old  Idria  furnace,  it  is  destined  to  disappear,  and  in  a 
few  years  will  probably  be  cited  as  one  of  the  curiosities  of  metal- 
history. 

CONTINUOUS  FURNACES. 

The  continuous  furnaces  in  use  are  all  of  them  shaft  furnaces, 
which  do  not  differ  essentially  in  the  principles  of  their  construction, 
though  there  are  wide  differences  of  detail,  which  are  more  or  less 
essential.  The  California  practice  is  essentially  different  from  that 
of  other  countries,  in  that  all  of  these  furnaces  are  provided  with 
fans  placed  beyond  the  condensing  apparatus,  which  not  only  do 
away  with  the  necessity  of  high  chimneys,  but  give  such  an  absolute 
control  of  the  draft  that  there  is  no  fear  of  the  fumes  escaping. 
The  draft  is  always  toward  the  interior  of  the  furnace,  so  that 
even  if  an  aperture  in  the  furnace  or  the  condensing  apparatus 
should  remain  open,  no  fumes  escape,  and  consequently  cases  of 
salivation  are  very  rare.  As  the  velocity  of  the  fan  can  always 
be  changed,  the  draft  can  be  regulated  at  will  to  suit  either  the 
working  of  the  furnace,  or  the  irregularities  of  the  weather.  The 
furnace  is  of  less  consequence  than  the  condensation  apparatus, 
though  its  aim  should  always  be  to  extract  the  metal  at  the  lowest 
possible  temperature,  and  to  require  the  least  possible  preparation  of 
the  ore.  It  is  consequently  on  the  condensation  apparatus  rather 
than  on  the  furnace  that  the  greatest  number  of  experiments  have 
been  made;  providing  that  the  furnaces  are  continuous,  the  one 
which  has  the  best  condensation  apparatus  will  be  the  best. 

There  are  a number  of  these  furnaces  used  in  California,  all  of 
which  I believe  are  patented.  I saw,  however,  but  two  of  them, 
the  Luckhart  and  the  Knox,  working. 

LUCKHART  FURNACE. 

The  Luckhart  furnace  is,  in  all  respects,  similar  to  the  Swedish 
furnace  for  roasting  iron  ores.  It  consists  of  a shaft  with  a fire-box, 
with  openings  in  the  two  sides  only,  which  goes  through  the  furnace 
from  one  side  to  the  other.  It  is  covered  with  a cast-iron  roof  slant- 
ing from  the  centre  towards  both  sides  of  the  furnace,  so  that  the 

3 


20 


NOTES  ON  THE  TREATMENT 


charge  is  divided  as  it  passes  down,  and  the  heat  is  also  divided  as 
it  passes  up.  The  sides  of  the  furnace  are  pierced  with  holes  to  ob- 
serve what  is  passing  in  its  interior,  and  to  watch  the  progress  of  the 
charge.  The  discharge  door  is  sufficiently  far  below  the  grate  to 
insure  the  ore  remaining  long  enough  in  the  furnace  to  have  all 
of  its  volatile  contents  distilled,  and  to  be  sufficiently  cool  to  be 
discharged  with  perfect  safety  into  an  open  wagon  at  the  bottom. 
By  this  system,  which  is  common  to  all  the  continuous  furnaces,  the 
inconveniences  arising  from  the  discharge  of  hot  ore  not  entirely 
worked  are  avoided. 

The  Luckhart  furnace  used  at  the  Sonoma  mine,  is  capable  of 
treating  15  to  18  tons  of  ore  and  adobes  a day.  The  richest  ore 
treated  has  not  contained  over  10  per  cent.  The  serpentine  contain- 
ing the  mercury  crops  out  near  the  furnace,  and  is  very  much  decom- 
posed. The  rock  is  soft  and  crumbly,  and  where  it  is  exposed  to  the 
weather,  its  debris  have  been  washed  away  so  that  the  soil  for  some 
distance  from  the  outcrop  is  composed  of  its  detritus,  more  or  less 
mixed  with  free  mercury,  and  a very  little  undecomposed  cinnabar. 
Where  the  rock  has  been  mined  so  as  to  reach  the  undecomposed 
parts  of  it,  it  is  found  to  contain  in  the  upper  portions  more  or  less 
free  mercury  mixed  with  the  cinnabar,  but  nine-tenths  of  all  the  ore 
treated  consists  of  dirt  taken  from  the  surface  of  the  ground,  which 
is  made  into  adobes  by  Chinamen,  The  adobes  contain  from  one- 
quarter  to  one-half  per  cent.  The  rock  does  not  contain  more  than 
one  and  a half  per  cent.  The  adobes  are  made  by  mixing  the  earth 
with  water  to  a thick  paste,  and  then  putting  it  into  wooden  moulds 
5 by  4J  inches,  and  4 inches  high.  The  thick  mud  is  simply  placed 
in  a frame  containing  8 of  these  moulds,  patted  with  a shovel,  the 
wooden  frame  drawn  up,  and  the  adobes  left  to  dry  in  the  sun ; it 
takes  about  two  days  to  dry  them.  When  ready  for  use,  they  weigh 
about  eight  pounds  each,  and  are  a little  larger  than  an  ordinary 
brick.  One  Chinaman  can  make  a thousand  in  a day.  The  men 
are  paid  $1.25,  and  find  themselves.  It  takes  two  Chinamen,  at 
$1.25,  to  pick  as  much  dirt  as  six  men  can  use  for  making  adobes. 

The  furnace  is  charged  by  means  of  a circular  hopper  22  inches  in 
diameter,  and  26  deep  ; 5 to  6 of  these  hoppers  full  make  a charge, 
and  5 such  charges  make  a ton.  The  hopper  is  covered  over  with  a 
hydraulic  cover  for  safety,  but  even  when  it  is  off,  the  draft  is  so 
strong  that  there  is  no  discharge  of  mercurial  vapors  from  the  top 
of  the  furnace,  as  I assured  myself  by  removing  the  cover  and  hav- 
ing the  charge  withdrawn  below  the  hopper.  The  furnace  consumes 
one  and  a half  cords  of  wood  a day,  which  comprises  all  the  fuel 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


21 


used  in  the  works.  The  wood  is  usually  oak,  and  is  worth  $3  a 
cord.  About  15  tons  of  ore  a day  are  treated.  Most  of  the  ore  is 
discharged  from  the  bottom  of  the  furnace  black,  some  of  the  last  of 
a discharge  is  occasionally  red-hot  ; it  is  drawn  about  every  hour 
and  a quarter  into  iron  wagons,  which  hold  about  half  a ton.  There 
are  7 men  engaged  in  making  adobes,  and  there  is  one  Chinaman 
and  one  engineer  on  each  shift  of  twelve  hours  at  the  furnace ; the 
Chinaman  is  paid  $1.50,  and  finds  himself,  the  engineer  is  paid  $65 
a month.  The  engineer  helps  the  Chinaman,  who  draws  the  charge 
and  dumps  it,  and  charges  the  furnace  and  puts  in  the  fuel.  In  ad- 
dition to  the  two  helpers,  there  is  one  man  engaged  continually  in 
chopping  wood.  The  total  cost  of  treating  the  ore  is  one  dollar  per  ton. 

The  condensing  apparatus  consists  of  three  sheet-iron  cylinders 
five  feet  apart,  which  are  14  feet  high,  6 feet  in  diameter.  The  va- 
pors pass  from  the  furnace  through  a pipe  about  20  feet  long,  in  at 
the  top,  and  out  at  the  bottom  of  the  condenser.  A blower  is  placed 
just  beyond  the  last  condenser,  which  is  three  feet  in  diameter,  and 
makes  100  to  120  revolutions  a minute.  If  there  is  much  fine  stuff 
not  made  into  adobes  charged  into  the  furnace,  it  must  be  run  faster. 
The  engine  used  is  twelve  horse-power,  but  six  would  answer  for  a 
single  furnace.  Just  beyond  it  is  a wooden  box,  6 feet  high,  12  feet 
long,  and  8 feet  wide,  into  which  the  blower  discharges.  This  box 
has  a partition  in  the  centre,  which  goes  to  within  2 feet  of  the  bot- 
tom, to  break  the  current.  From  this  box  there  is  a flue  2 feet  square, 
and  100  feet  long,  ending  in  a wooden  chimney  20  feet  high.  Around 
the  top  of  the  condensing  cylinders  there  is  a lead  pipe  1 inch  in 
diameter,  pierced  with  small  holes  about  3 inches  apart.  When 
there  is  a plenty  of  water  it  is  allowed  to  flow  continuously  from  this 
pipe,  and  discharges  itself  over  the  outside  of  the  cylinder,  thus 
cooling  it.  When  there  is  a lack  of  water  it  is  allowed  to  flow  only 
over  the  last  condenser.  The  pipes  which  connect  the  cylinders 
have  in  their  interior  a partition  about  2 feet  long,  and  on  them 
a considerable  amount  of  soot  collects.  The  bottom  of  the  cylin- 
ders incline  towards  the  centre,  and  from  here  a pipe  leads  to  an 
iron  kettle  on  the  outside  two  feet  in  diameter,  which  is  kept 
constantly  full  of  water.  A large  quantity  of  soot  collects  on  the 
sides  of  the  condensing  apparatus.  A little  of  it  constantly  falls, 
and  is  washed  out  into  the  iron  basin  by  the  condensed  moisture, 
which  is  but  slightly  acid,  as  there  is  but  little  cinnabar  in  the  ore. 
About  one  flask  of  mercury  a day  is  collected  from  the  first  two 
condensers.  About  one-half  of  this  comes  from  the  second.  From 
the  third  about  a flask  a month  is  collected.  The  cylinders  are  pro- 


22 


NOTES  ON  THE  TREATMENT 


vided  with  doors,  and  the  furnace  is  stopped  once  in  three  weeks  to 
clean  out  the  soot,  which  is  collected  in  kettles.  About  ten  flasks  of 
mercury  will  collect  from  the  soot  after  some  stirring ; the  rest  is  put 
into  an  iron  pan,  9 feet  by  3,  with  a gutter  in  the  centre.  The  pan 
is  set  at  an  angle  of  20°,  and  gently  heated  to  about  120°  F. ; it  is 
then  mixed  with  lime  or  ashes  and  stirred.  The  mercury  flows 
readily  from  it,  and  about  70  per  cent,  of  its  mercury  contents  is 
collected  in  this  way.  The  resi  is  made  into  adobes  and  treated  in 
the  furnace. 

The  more  or  less  acid  water  which  is  constantly  flowing  into  the 
basin  outside  of  the  condenser,  as  it  runs  off  carries  away  some  light 
mercury  and  soot.  This  is  conducted  to  a wooden  tank,  12  feet  long, 
6 feet  wide,  and  4 feet  deep,  where  it  collects  and  gives  a product 
which  contains  considerable  mercury,  which  is  treated  as  soot.  The 
soot  comes  from  the  basins,  the  wooden  tanks,  and  sometimes  a very 
little  is  taken  from  the  blower  cylinders.  This  soot  gets  poorer  as 
it  is  further  from  the  furnace.  The  richest  contains  60  per  cent,  of 
mercury  and  the  poorest  about  3.  The  product  of  the  works  is 
about  25  to  50  flasks  of  mercury  a month. 

The  condensation  at  these  works  seemed  nearly  perfect.  The  man- 
ager stated  to  me  that  he  had  exposed  a $20  gold  piece  for  six  weeks 
from  the  top  of  the  wooden  chimney,  and  that  he  not  only  found  it 
there  at  the  end  of  that  time,  but  entirely  unaffected  by  mercury. 
There  is  so  little  sulphur  in  the  ore  that  the  sheet  iron  does  not  seein 
to  have  been  acted  upon  to  any  great  extent.  With  this  system  of  high 
cylinders  with  a bottom  converging  towards  the  centre,  there  seems  to 
be  but  little  opportunity  for  the  action  of  the  acid,  and  with  a thick 
cast-iron  bottom  there  seems  to  be  no  reason  why  it  should  not  answer 
quite  well.  It  would  seem,  however,  that  a few  large  compartments 
could  not  give  as  good  results  as  a greater  number  of  smaller  ones, 
as  a perfect  condensation  requires  a maximum  of  surface,  and  does 
not  depend  so  directly  upon  volume,  though  the  amount  of  soot 
and  mercury  collected  in  the  wooden  box  and  in  the  last  condenser 
here  seem  to  show  that  in  this  case,  at  least,  owing  probably  to  the 
very  small  product  of  the  furnace,  the  condensation  was  quite  perfect. 

KNOX  FURNACE. 

At  Knoxville,  beside  the  Idria  furnaces,  there  were,  in  August, 
1874,  at  the  Redington  mine,  two  Knox  furnaces  in  the  course  of 
construction,  and  two  in  work,  which  treated  25  tons  of  ore  each  in 
twenty-four  hours,  and  have  been  running  since  January,  1874. 
During  the  years  1874  and  1875,  two  other  furnaces  have  been  con- 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


23 


structed,  making  six  in  all,  which  treat  together  from  900  to  1000 
tons  of  ore  a week.  Before  the  use  of  these  Knox  furnaces,  and 
while  the  modified  Idria  furnaces  were  the  only  ones  in  use  at  these 
works,  all  the  ore  had  to  be  dressed  up  to  5 per  cent.  Now  ore 
yielding  not  more  than  1 to  1 J per  cent.,  as  it  comes  from  the  mine, 
is  treated,  and  Mr.  Knox  claims  that  he  can  treat  profitably  ore  con- 
taining not  more  than  J per  cent.  A furnace  about  to  be  con- 
structed is  to  be  adapted  to  treat  fine  ore  exclusively,  and  it  is  ex- 
pected, if  this  furnace  wTorks  successfully,  to  give  up  making  adobes 
altogether  and  treat  the  fine  ore  here,  and  if  the  modified  Idria  fur- 
naces are  still  retained,  to  treat  in  them  only  the  large  and  medium- 
sized ores. 

The  Knox  furnace  (Figs.  1,  3,  4,  and  5)  is  a shaft  furnace  with 
a fireplace  upon  the  side.  The  total  height  of  the  furnace  is  39 
feet.  The  bottom  of  the  fireplace  is  17  feet  6 inches  from  the 
bottom  of  the  furnace,  so  that  the  fire  itself  is  about  in  the  middle 
of  the  shaft.  The  furnace  is  rectangular  in  shape.  At  the  top  it  is 
2 feet  square ; it  continues  for  2 feet  at  this  size,  and  then  widens  out 
• on  one  side,  until  at  the  depth  of  4 feet  it  attains  the  width  of  7 feet. 
While  in  the  other  direction  it  continues  straight  for  a depth  of  10 
feet,  and  then  increases  gradually  until  it  becomes  7 feet  at  the  fire- 
place. At  this  point  there  are  two  chambers,  Z and  Z',  Fig.  5, 
arranged  in  the  masonry,  on  one  side  for  the  fireplace,  and  on 
the  other,  the  space  for  the  introduction  of  the  pipe  U',  which 
carries  off  the  fumes.  At  this  point,  which  is  17  feet  6 inches 
from  the  top,  there  commence  a series  of  six  retreating  arches, 
which  support  the  masonry  of  the  furnace,  four  of  which  retreat 
2 feet  6 inches  on  either  side.  The  two  others  which  are  above  are 
much  smaller,  and  reach  to  within  3 feet  of  the  top  of  the  furnace. 
At  the  fireplace  the  furnace  is  7 feet  square.  The  shaft  continues  to 
the  bottom  on  the  fireplace  side  of  the  same  size.  On  the  other 
side  it  contracts  equally  upon  both  sides,  so  that  at  the  bottom, 
X Y,  where  the  ore  discharges,  the  width  is  only  2 feet.  The  fire- 
place follows  the  retreating  arches  with  a width  of  36  inches  to  the 
top  of  the  second  arch,  and  then  diminishes  to  30  at  the  top  of  the 
third,  and  continues  so  to  within  3 feet  6 inches  of  the  top  of  the  fur- 
nace. Between  each  of  these  arches,  on  both  sides  of  the  furnace, 
there  are  openings  6 inches  wide,  and  the  whole  width  of  the  arch. 
The  aspiration  of  the  blower  draws  the  flame  from  the  fireplace  Z 
to  the  chamber  Z'  on  the  opposite  side.  The  heat  of  the  fireplace 
is  always  sufficient  to  keep  it  at  a dull-red.  This  construction  of 
the  fireplace  is  far  too  complicated.  These  retreating  arches  are 


24 


NOTES  ON  THE  TREATMENT 


liable  to  be  worn  by  the  ore,  though  not  very  rapidly,  but  are  quite 
rapidly  affected  by  the  fire  and  the  gases.  Exactly  the  same  effect 
might  be  brought  about  by  the  much  simpler  construction  of  having 
the  fireplace  entirely  outside  of  the  furnace.  As  originally  con- 
structed the  furnace  was  quite  different.  It  was  24  x 42  inches  at 
the  top,  and  continued  for  2 feet  at  this  size,  and  then  gradually 
widened  by  a curve  upon  one  side  until  at  a depth  of  7 feet  from 
top  it  was  7 feet  6 inches  wide  f it  continued  to  the  bottom  of  the 
fireplace  at  this  width,  and  then  gradually  diminished  until  it  was  2 
feet  at  the  discharge.  On  the  other  side,  at  a depth  of  2 feet  from 
the  top,  it  widened  to  3 feet,  and  continued  at  this  width  to  the  top 
of  the  arch,  then  followed  the  retreating  arches  down  to  the  bottom 
of  the  fireplace,  where  it  was  7 feet,  and  continued  at  this  size  to  the 
discharge.  There  were  only  three  openings  between  the  arches,  and 
it  was  found  that  this  was  insufficient,  and  the  two  small  arches 
above  were  introduced  to  increase  the  heat  and  attack  the  ore  higher 
up.  The  fireplace  is  so  arranged  that  it  receives  air  which  enters 
at  the  bottom  of  the  furnace  and  passes  round  it  through  a series  of 
channels  Y,  so  that  before  entering  the  fireplace,  it  is  heated  by  the  • 
walls  of  the  furnace,  and  thus  effects  a small  saving  in  fuel,  so  that 
the  furnace  may  be  said  to  be  in  some  respects  a hot-air  furnace. 
The  masonry  of  the  furnace  was  formerly  made  6 feet  thick,  and  it 
is  now  made  8 feet.  It  is  braced  by  ten  large  wooden  beams,  which 
are  held  together  by  iron  bolts,  and  as  the  furnace  is  double,  are 
strengthened  by  three  uprights  of  the  same  size,  also  clamped  to- 
gether by  bolts  which  pass  entirely  through  the  masonry  furnace. 
By  the  enlargement  of  the  furnace  in  the  centre  the  ore  as  it  comes 
to  the  point  where  it  is  to  receive  the  highest  temperature  is  made 
suddenly  to  spread  out,  so  that  each  particle  of  it  comes  in  contact 
with  the  heat,  and  is  in  no  danger  of  fusing.  The  flames  are  made 
to  traverse  through  the  six  openings  between  the  arches,  which  are  6 
inches  in  height,  to  the  chamber  on  the  opposite  side  of  the  furnace, 
into  which  all  the  fumes  are  carried  by  the  draft. 

The  cubic  contents  of  the  furnace  is  calculated  in  such  a way  as  to 
be  capable  of  containing  about  75  tons  of  ore,  bqt  as  only  1 ton  of 
treated  ore  is  drawn  from  the  bottom  of  the  furnace  every  hour  its 
capacity  is  24  tons  in  twenty-four  hours,  so  that  every  ton  of  ore 
will  remain  in  the  furnace  at  least  three  days.  When,  however,  the 
proportion  of  very  fine  ore  becomes  large,  or  when  the  ore  is  wet, 
the  amount  that  can  be  treated  in  twenty-four  hours  will  be  reduced 
to  12  to  16  tons  per  day.  In  the  case  of  a large  quantity  of  fine 
ore  it  is  proposed  to  remedy  this  to  some  extent  by  charging  wood  in 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


25 


small  pieces  with  the  ore.  This  serves  to  some  extent  the  purpose 
of  keeping  the  ore  open,  so  as  to  allow  free  passage  to  the  heat 
through  the  ore,  and  at  the  same  time  creates  a source  of  heat  within 
the  charge,  so  that  it  will  be  partially  dried,  and  not  pack  as  it  comes 
down  in  front  of  the  fireplace.  The  chamber  for  the  outlet  of  the 
vapor  is  underlaid  with  a very  heavy  cast-iron  plate,  in  order  to  pre- 
vent any  possible  condensation  or  absorption  of  the  vapor  at  that 
point.  The  pipe  U'  for  the  outlet  of  gas  is  made  of  cast  iron,  is 
18  inches  in  diameter,  16  feet  in  height,  as  it  enters  the  condensation- 
chambers  U.  It  projects  2 feet  from  the  furnace  before  it  turns 
down  ; at  the  elbow  there  is  a man-hole  for  cleaning  the  pipe.  Just 
above  the  outlet  pipe  a cast-iron  door  is  arranged,  so  as  to  observe 
what  is  passing  in  the  interior  of  the  furnace  on  the  side.  Two  of  the 
furnaces  were  built  in  one  structure  on  account  of  economy  of  con- 
structing and  running  them.  They  are  charged  with  f to  f medium, 
and  J to  J of  fine  ore.  Adobes  are  never  used  in  these  furnaces. 

The  charge  is  introduced  by  means  of  an  automatic  iron  wagon, 
which  contains  18  cubic  feet  of  ore,  which  is  equivalent  to  about  a 
ton  when  it  is  moderately  heaped.  If  the  ore  is  very  light,  how- 
ever, the  amount  contained  may  be  somewhat  less  than  this.  When 
the  capacity  of  the  furnace  is  given  in  tons,  that  number  of  carloads 
is  intended  to  be  expressed.  The  wagon  runs  upon  rails,  and  is 
shoved  by  the  charger  to  the  top  of  the  furnace,  where  the  rim  of 
the  wagon  first  strikes  a lever  attached  to  a wire  rope,  which  sup- 
ports the  cover  of  the  furnace,  which  throws  off  the  cover,  then 
a projection  on  the  body  of  the  wagon  throws  it  to  one  side.  The 
workman  then  pulls  out  a pin  in  the  wagon,  which  discharges  the 
ore  into  the  furnace.  As  soon  as  the  ore  is  discharged  the  weight  of 
the  furnace  top  and  lever  drives  the  car  back,  when  the  cover  drops 
and  closes  the  furnace.  The  weight  of  the  charge  holds  the  wagon 
in  place  only  long  enough  for  the  car  to  empty  itself.  The  work- 
man shoves  the  empty  car  back  far  enough  to  be  out  of  the  wTay, 
covers  the  furnace  top  with  ashes,  and  prepares  a new  charge. 

There  are  fifteen  men  breaking  and  sorting  the  ore,  but  one  man 
does  the  whole  charging  for  both  furnaces.  The  fuel  used  here  and 
at  the  Manhattan  works  is  the  most  ordinary  oak  brush,  which  is  cut 
by  the  company  and  brought  one-quarter  of  a mile.  It  costs  about  $4 
a load,  which  is  supposed  to  be  equal  to  about  a cord  of  good  wood. 
The  reason  for  the  use  of  brushwood  is,  that  during  the  summer  an 
unlimited  supply  of  it  can  be  had  at  a short  distance  from  the  fur- 
nace, both  at  the  Manhattan  works  and  at  Knoxville.  It  is  much 


26 


NOTES  ON  THE  TREATMENT 


more  easily  cut  and  carried  than  wood,  and  it  is  a cheap  fuel  in  the 
summer.  As  this  supply  fails  in  the  winter,  and  teaming  is  more 
difficult,  wood  is  used  at  this  season.  A sheet-iron  trough,  3 feet 
long  and  2 feet  square,  is  hung  before  the  fireplace  door.  This 
trough  is  made  to  fit  the  fireplace  door,  which  is  counterbalanced  and 
rises  vertically.  The  brush  is  cut  to  the  length  of  the  trough  and  is 
packed  into  it  with  a pitchfork,  the  fire-place  door  is  then  raised,  and 
the  brush  shoved  in  with  the  fork.  This  brush  is  used  green,  im- 
mediately after  cutting.  It  flames  very  readily  and  makes  a quick 
hot  fire.  It  is  charged  about  every  half  hour.  It  takes  2J  cords 
of  good  wood  to  do  the  work  of  the  furnace  in  twenty-four  hours, 
or  two  loads  of  brush,  which  are  considered  as  weighing  one  ton. 
The  wood  is  a mixture  of  white  and  live  oak,  and  costs  $5  a cord 
delivered  at  the  furnace.  A ton  of  the  brushwood  costs  $5,  and  is 
sufficient  to  treat  about  24  tons  of  ore. 

The  fireman  draws  the  ore  that  has  been  treated  and  takes  care  of 
the  furnade.  The  charge  is  drawn  from  a long  narrow  door  X in  the 
lower  part  of  the  furnace,  15  feet  below  the  level  of  the  fireplace  and 
on  the  side  next  to  it.  The  door  is  raised  by  a tackle,  and  is  counter- 
poised. The  discharge  is  effected  by  means  of  a hoe  and  a rake, 
attached  to  handles  12  to  14  feet  in  length  made  of  inch  pipe.  The 
discharging  car  is  of  iron,  and  is  half  the  length  of  the  door.  It  is 
rolled  to  one  side  of  the  opening  and  stopped  with  the  handle  of 
the  rake,  So  as  to  be  exactly  opposite  the  end  of  the  door.  The  ore, 
which  is  black,  though  not  cold,  is  drawn  into  it  from  one  side  of 
the  charging  door  until  the  wagon  is  half  full,  it  is  then  rolled  to 
the  other  side  and  filled  from  there.  By  the  time  the  car  is  full  the 
red-hot  ore  appears.  The  car  holds  one  ton  of  fully  treated  ore. 
One  load  is  drawn  every  hour  from  each  furnace.  The  furnace  is 
charged  above  as  soon  as  the  charge  is  drawn.  It  is  done  by  the 
same  men  who  also  attend  to  the  fire. 

Each  furnace  requires  two  men  and  an  aid  per  shift,  so  that  a 
single  furnace  requires  six  men  to  treat  24  tons  in  24  hours.  A 
double  furnace  requires  only  8 men,  who  trekt  5 tons  in  24  hours. 
To  run  four  furnaces,  standing  as  in  Plate  VIII,  requires  10  men 
to  treat  100  tons  in  24  hours.  It  therefore  requires  one  day’s 
labor  to  treat  4 tons,  6 tons,  or  10  tons  in  24  hours,  showing  a 
gain  of  twice  and  a half  on  all  the  labor  by  increasing  the  number 
of  furnaces  to  four.  One  engine  and  boiler  will  do  all  the  work  of 
four  furnaces,  and  three  or  four  cords  of  wood  is  sufficient  both  to 
burn  the  ore  and  to  keep  up  steam  to  run  the  blowers. 


OF  MEECUBY  IN  NOETH  C ALIFOENI A . 


27 


The  draft  in  the  furnace  is  produced  by  four  Root’s  blowers,  E, 
F,  G,  H,  placed  at  the  extremity  of  the  condensing-chambers.  The 
bottoms  of  the  condensers  U are  inclined  at  an  angle  of  from  15° 
to  20°.  They  are  joined,  as  is  shown  in  the  drawings,  at  the  top  by 
means  of  curved  iron  pipes  Uk  There  are  sixteen  to  each  furnace 
as  at  present  constructed.  It  is  proposed,  however,  to  have  four 
sets  of  eleven,  two  sets  of  ten,  and  six  out  of  line,  making  twenty- 
two  in  all,  or  eighteen  for  each,  when  the  four  furnaces  are  finished.  * 
These  condensers  are  8 feet  long,  2 feet  6 inches  wide,  and  5 feet 
high  at  one  end  and  6 feet  at  the  other.  They  are  set  on  wooden 
frames  on  a cement  floor.  The  first  condenser  of  the  series  nearest 
the  furnace  is  set  30  inches,  and  the  last  one  37  inches  above  the 
ground.  Commencing  with  the  next  series,  the  first  one  farthest 
from  the  furnace  is  40  inches,  and  the  last  one  of  this  series,  near- 
est to  the  furnace,  is  47  inches  above  the  ground.  They  are  made 
out  of  three  castings,  for  greater  ease  of  transportation  and  repair. 
The  top  piece  is  30  inches  in  depth  all  round,  is  clamped  to  a 
projection  of  the  bottom  part.  The  top  is  made  in  the  shape  of  a 
pan,  and  holds  water  to  the  depth  of  2 inches.  When  there  is 
plenty  of  water  it  is  made  to  discharge  over  the  top,  so  as  to  run 
down  the  sides  of  the  condensers,  but  when  water  is  scarce  it  simply 
rests  upon  the  top.  At  the  Manhattan  works,  which  were  the 
first  that  used  the  Knox  furnace,  the  condensers  are  only  half 
the  height  of  those  used  elsewhere.  They  have  been  in  constant 
use  for  five  years,  and  are  nearly  worn  out,  though  they  may  last 
six  months  or  a year  longer.  The  ore  here  does  not  contain  much 
sulphur.  These  condensers  will  be  replaced  by  others  like  those  in 
use  here.  A very  small  amount  of  weak  and  impure  sulphuric  acid 
water  commences  to  condense  in  the  third  condenser,  but  is  very 
abundant  in  the  eighth,  and  condenses  through  all  the  rest.  It 
corrodes  the  iron-work  more  or  less  rapidly.  As  this  action  takes 
place  chiefly  on  the  bottom  of  the  condenser,  it  is  cast  separate  and 
made  several  inches  thick.  As  it  has  been  found  that  the  action  of 
the  acid  water  is  much  less  rapid  when  it  is  in  contact  with  a small 
quantity  of  air,  it  is  allowed  to  collect  for  about  two  inches  in  the 
bottom  of  the  last  eight  condensers,  and  at  this  height  is  discharged 
from  a wooden  spout  into  the  mercury  trough,  and  runs  to  the  set- 
tling vats  M,  which  are  6 by  10  feet  in  size  and  4 feet  deep.  A very 
small  amount  of  mercury  is  carried  otf  by  these  streams  and  collects 
in  this  tank.  The  very  small  amount  so  collected  shows  that  the  con- 
densation is  very  nearly  perfect.  Mercury  commences  to  collect  in 


28 


NOTES  ON  THE  TEE  ATM  ENT 


the  first  to  the  eighth  condenser,  and  is  discharged  at  once  into  a 
conduit  by  a small  opening  in  the  bottom  of  the  manhole  door.  It 
is  collected  in  the  iron  pots  K,  which  contain  about  an  inch  of 
water,  to  prevent  the  mercury  from  spattering  as  it  falls  into  the 
pot.  The  iron  pipe  leading  from  the  trough  into  the  mercury  pot 
is  shaped  like  a goose-neck,  so  that  the  acid  water  runs  olf  above 
and  the  mercury  collects  clear.  Tt  is  bottled  from  these  pots  in  the 
* bottling-pot  J. 

From  the  end  of  each  set  of  condensers  a wooden  box,  E',  F',  G', 
H',  1500  feet  long  and  30  inches  square,  carries  the  fumes  and 
smoke  away  from  the  furnace.  The  boards  of  which  it  is  made  are 
clamped  against  a wooden  frame,  on  the  inside  by  wooden  clamps,  on 
the  outside  so  that  it  can  be  taken  apart  at  any  time.  If  nails 
were  used  they  would  very  quickly  corrode,  and  the  flue,  if  not 
clamped,  would  be  likely  to  fall  to  pieces  at  any  moment.  300  feet 
from  the  furnace,  on  these  long  flues,  there  is  a chimney,  I,  which 
descends  about  15  feet  high  and  4 feet  square.  This  chimney  is  filled 
with,  large  stones,  and  water  is  made  to  flow  over  them  from  a pipe 
connecting  with  the  reservoir  S.  This  reduces  the  volume  of  smoke, 
which,  in  this  way,  is  made  quite  cool  at  this  point.  1000  feet  from 
this  point  the  four  conduits  are  united  into  one,  and  is  continued  to 
the  top  of  the  hill,  half  a mile  off.  No  mercury  and  no  mercurial 
soot  is  found  in  any  part  of  this  conduit,  or  in  the  flues  leading  to  it. 
The  object  of  it  is  to  carry  away  the  smoke,  which  in  the  winter- 
time collects  in  and  around  the  furnace  and  annoys  the  men.  It 
is  quite  common  to  see  the  sickly  cattle  of  the  neighborhood  collect 
near  the  end  of  this  conduit  and  remain  there  for  half  a day  at  a 
time,  so  that  they  have  to  be  driven  from  it. 

The  engines,  W,  which  do  the  work  of  the  two  blowers  are  fifteen 
horse-power,  and  are  to  be  used  to  saw  all  the  wood.  It  takes  re- 
cords of  wood  for  the  engines  in  twenty-four  hours.  Nothing  like 
fifteen  horse-power  is  required  for  these  blowers,  and  only  four  will 
be  required  when  the  six  furnaces  are  built.  ' 

All  the  condensers  are  cleaned  once  a week.  This  is  done  in  the 
intervals  between  the  charging  and  discharging  by  taking  off  the 
manhole  door  and  cleaning  down  the  sides  with  a hoe,  but  without 
scraping  them.  It  takes  two  to  three  minutes  to  take  out  the  soot 
from  each  condenser.  The  soot  is  caught  in  an  iron  soot-bucket, 
which  is  2 feet  by  3 feet,  and  18  inches  deep,  and  is  carried  on  a 
truck. 

The  soot  from  the  first  eight  condensers  only  is  rich  enough  to 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


29 


treat ; that  collected  from  the  others  is  too  poor  to  work,  and  is  put 
back  into  the  furnace.  The  draft  into  the  condenser  is  so  strong 
that  there  is  no  danger  that  mercurial  vapors  will  escape,  if  not  more 
than  one  condenser  is  open  at  a time ; so  that  to  prevent  any  pos- 
sible accident  they  are  opened  one  by  one.  After  one  or  two  have 
been  cleaned  the  soot  is  worked  up,  and  then  the  others  are  cleaned. 
By  doing  the  work  in  this  way  times  can  be  selected  when  the  fur- 
nace is  neither  charging  or  discharging.  The  quantity  of  soot  which 
is  produced  is  very  variable,  and  depends  entirely  upon  how  thor- 
oughly the  condensers  are  cooled,  whether  the  fire  is  slow  or  quick, 
upon  the  speed  of  the  blower,  and  also  to  some  extent  upon  the 
changes  of  the  weather,  so  that  the  quantity  deposited  in  each  con- 
denser will  vary  at  different  times.  The  same  is  true  of  the  acid 
water ; and  it  sometimes  happens  that  when  the  blower  is  run  at 
the  usual  speed,  and  everything  else  in  the  furnace  is  in  the  normal 
condition,  but  the  water  has  given  out,  that  no  acid  water  will  be 
deposited  in  the  first  six  or  eight  condensers,  the  heat,  which  is  usu- 
ally absorbed  by  the  evaporation  of  the  water,  being  so  great  that 
they  remain  perfectly  dry. 

It  takes  from  Monday  to  Friday  to  clean  out  and  work  up  all  the 
soot,  which  is  worked  in  the  usual  way  with  lime  on  an  inclined 
plane. 

On  Saturday  the  conduit  and  spouts,  which  get  filled  with  mud, 
are  cleaned,  and  the  flasks  are  filled  with  mercury  collected  during 
the  week.  In  a charge  which  gives  150  flasks  per  week,  40  flasks 
come  from  the  soot. 

The  works  are  so  arranged  that  two  furnaces  may  be  run  with 
one  blower,  or  through  one  set  of  condensers ; and  this  may  become 
necessary  when  one  of  the  blowers,  or  one  set  of  the  condensers, 
have  to  be  repaired.  It  is  more  difficult  to  keep  the  heat  up  under 
such  circumstances,  and  a smaller  charge  has  to  be  put  into  each 
furnace.  The  diminution  of  capacity  will  amount  to  from  four  to 
five  car-loads  of  ore  in  twenty -four  hours.  The  two  furnaces,  B and 
C,  will  generally  treat  50  tons  of  assorted  ore  in  a day.  They  have 
been  run  without  repairs  since  January,  1874,  and  have  produced 
from  600  to  900  flasks  a month,  the  variation  depending  upon  the 
richness  of  the  ore. 

It  is  the  intention  to  make  the  trial  of  distilling  all  the  soot  in  a 
retort,  P.  The  retort  is  built,  but  the  trial  had  not  at  the  time  of 
my  visit  been  made. 

At  the  Manhattan  works  the  soot  is  worked  up  in  a retort  to 


30 


NOTES  ON  THE  TREATMENT 


which  a Liebig  condenser,  like  Q,  10  feet  long,  is  attached.  The 
condensing  pipe  is  large  enough  to  hold  a barrel  of  water  at  one  time. 

The  experiment  is  being  made  here  of  working  the  soot  mechani- 
cally. It  is  mixed  with  lime  and  is  put  into  an  iron  rocker,  which 
has  several  motions,  and  in  which  a rake  works  backwards  and  for- 
wards. A very  large  part  of  the  mercury  in  the  soot  is  collected  in 
this  way  by  machine  labor  withjfit  necessarily  having  any  one  to 
tend  it.  The  rocker  is  run  by  the  steam-engine  of  the  works. 
This  machine  is  not  yet  perfected.  Working  as  it  did  at  the  time  of 
my  visit,  some  of  the  mercury  separated  is  afterwards  flowered. 
This  is  a serious  imperfection,  but  it  is  expected  will  be  shortly  over- 
come. 

The  best  men  in  the  works  at  Knoxville  are  always  selected 
for  the  Knox  furnace.  They  work  twelve  hours,  and  are  paid  $40 
for  30  days  and  board.  If  the  men  have  families  and  occupy  the 
company’s  cottages  they  are  allowed  $20,  as  a commutation  for 
board,  but  they  pay  $7J  per  month  for  rent. 

California  Works. 

The  California  Quicksilver  Works  also  use  the  Knox  furnace. 
They  treat  their  own  ores  and  produce  26  flasks  of  76 J pounds  of 
mercury  a week.  All  the  ore  passes  over  a coarse  screen,  so  as  to 
separate  the  large  pieces  from  the  fine  and  small,  which  are  separated 
by  other  screens  in  the  same  shute.  The  larger  pieces  are  broken 
by  hand.  The  fine  ore  which  is  rich  enough  is  made  into  adobes. 
One  man  mixes  his  dirt  and  makes  900  a day.  The  poor  fine  ore 
is  dressed  by  hand  gigs,  and  six  men  treat  10  tons,  and  reduce  it  to 
one-eighth  of  its  former  capacity.  The  enriched  ore  contains  about 
five  per  cent  of  mercury,  but  a considerable  quantity  of  cinnabar  is 
lost  in  the  tailings,  and  it  is  doubtful  whether  the  dressed  ore  pays 
for  the  labor  expended  upon  it. 

The  men  are  paid  $40  and  board,  which  equals  $2  a day. 

The  attempt  was  made  here  to  treat  the  soot  in  the  arched  chamber 
7J  opposite  the  fireplace,  but  the  gases  of  the  furnace  contained  so 
much  free  oxygen  at  this  point,  that  the  result  was  the  formation  of  a 
large  quantity  of  sulphate  of  mercury,  and  the  attempt  was  aban- 
doned, The  works  have  been  managed  with  so  little  care  that  the 
condensing-chambers,  which  have  been  used  only  18  months,  are  so 
corroded  that  they  will  have  to  be  taken  out.  Long  stalactites  of 
acid  sulphate  of  iron  are  hanging  from  them  in  every  direction,  and 
the  walls  in  some  cases  have  been  entirely  eaten  through,  or  are  so 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


31 


thin  that  they  could  be  easily  pushed  through  with  the  finger.  It 
is  the  intention  to  replace  the  last  eight  condensers  by  brick  chambers, 
8 by  10,  and  4\  feet  high,  with  three  partitions.  When  the  iron 
condensers  are  in  good  repair  the  soot  is  found  in  from  the  third  to 
the  sixth,  but  now  they  are  leaking  it  is  found  in  from  the  first  to 
the  third.  The  soot  is  drawn  every  week  from  the  first  six  con- 
densers ; beyond  the  sixth  they  are  cleaned  only  once  in  three  months. 
The  soot  collected  in  the  first  six  condensers  is  about  six  ordinary 
sugar  barrels  per  week.  The  quantity  depends  upon  the  sulphur  in 
the  ore,  its  dampness,  and  other  causes. 

Good  oak  wood  is  $4J  per  cord.  About  two  cords  in  twenty-four 
hours  are  burned  in  the  furnace.  Brushwood  is  not  as  cheap  as 
other  wood  here,  and  is  consequently  not  used.  There  are  five  men 
in  twenty-four  hours  about  the  furnace.  At  night  the  fireman  and 
engineer  alone  run  it. 

In  discharging  the  furnace  the  engineer  fills  the  wagon  while  the 
furnaceman  draws  the  charge  down.  In  the  daytime  there  is  a 
superintendent  of  the  work,  beside  one  man  making  adobes.  The 
miners  are  required  to  deliver  the  ore  broken  and  sorted.  There 
are  100  men  working  in  the  mines.  The  miners  are  paid  $45  a 
month.  The  works  have  been  run  constantly  for  18  months  with- 
out repairs,  and  have  not  stopped  more  than  three  weeks  during  the 
whole  of  this  time  for  any  cause. 

The  first  Knox  furnaces  constructed  cost  between  $35,000  and 
$40,000  each.  They  were  built  when  wages  were  high,  and  labor 
was  difficult  to  get.  The  furnaces  since  constructed  have  cost  about 
$25,000  each.  There  are  170,000  brick  in  the  furnace  beside  the 
stone,  but  nearly  half  the  cost  of  construction  is  for  iron- work. 

Below  is  a statement  of  the  cost,  at  the  Bedington  mine,  of  treat- 
ing the  ore  in  the  modified  Idria  furnace  and  the  Knox  furnace. 

Cost  per  ton  of  reducing  ore  in  the  modified  Idria  furnaces,  Nos. 
1 and  2,  at  the  Bedington  mine,  Napa  County,  California,  in  1874, 


taking  one  week’s  run,  both  furnaces : 

5^  cords  wood,  at  $5,  $24  50 

36  days.  Furnace  foreman  and  his  assistant,  . . . 86  00 

20  “ Laborers  charging  furnace, 38  60 

12  “ Laborers  discharging  furnace,  . . . 23  15 

8 “ Laborers  working  soot,  . . . . 14  55 

8 “ Fireman, 14  55 

9000  adobes,  at  $5  per  thousand, 45  00 


Total  charge  of  200  tons  ore  in  these  two  furnaces  cost  . $249  35 
Average  cost  per  ton  for  reduction, 1 25 


32 


NOTES  ON  THE  TREATMENT 


Cost  per  ton  of  reducing  ore  in  the  Knox  furnace  at  the  Redington 
mine,  furnaces  Nos.  3 and  4,  taking  one  week’s  run  of  both  furnaces : 


42  days’  labor,  engineer,  fireman,  soot  men,  etc.,  . . $81  06 

17|  cords  wood,  at  $5, 87  50 

1 gallon  oil  for  lamps, 75 

1 gallon  lard  oil  for  engine, 1 20 

v 

Total  cost  of  one  week’s  ruh, $170  51 

Average  cost  per  day  for  reducing  50  tons,  . . 24  36 

Average  cost  per  ton,  ......  50 


The  difference  between  $1.25,  which  is  the  cost  of  treatment  in 
the  modified  Idria  furnace,  and  $0.50  the  cost  of  treatment  in  the 
Knox  furnace,  is  sufficiently  great  not  only  to  warrant  the  use  of 
much  poorer  ore  in  the  latter  furnace,  but  to  call  seriously  into  dis- 
cussion whether  it  is  not  worth  while  to  abandon  the  old  style  of 
furnaces  altogether. 

Below  is  given  an  estimate  of  the  principal  items  of  expense  of 
building  one  Knox  & Osborn  quicksilver  furnace,  in  October,  1874: 


50  to  75  M red  brick. 

12  M fire-brick. 

Stone  for  foundation,  walls,  etc. 


1 cast-iron  lintel,  weight,  ..... 

. 3000  lbs. 

1 cast-iron  draw-door  frame,  weight,  . 

. 650 

it 

1 set  draw  plates,  cast  iron,  weight, 

. 3500 

a 

18  cast-irOn  condensers,  complete,  weight  each, 

. 6500 

It 

1 fire-door  and  frame,  weight,  .... 

. 650 

It 

1 flue-chamber  plate  and  door,  weight, 

. 1000 

tl 

6 braces,  weight, 

. 3000 

it 

1 blower-box,  weight,  ...... 

. 2500 

tl 

2 pots,  etc.,  weight,  ...... 

. 500 

It 

1 set  grate-bars,  weight,  ..... 

. 1200 

tl 

1 blower, 

. $500 

Blower  pipes,  ....... 

. $50 

1 retort  and  condenser, 

. $500 

1000  feet  wooden  flues,  cost  per  running  foot,  . 

. . . $1 

1 engine,  with  pulleys  and  shafting,  8x12  cylinder. 

2 boilers  (12  x 3). 

35  square  timbers,  12  inches  b}T  12  inches,  and  21  fbet  long. 

60  round  iron  rods,  1£  inch  diameter,  23  feet  long,  10-inch  washers 
on  both  ends. 

2 cars,  railroad  tracks,  etc. 

It  takes  six  or  eight  masons,  with  their  helpers,  between  three 
and  four  months,  to  build  one  of  these  furnaces.  The  cost  might  be 
made  less  by  making  more  than  one-half  of  the  condensers  of  wood. 
They  might  answer  even  nearer  the  furnace,  if  there  was  a certainty 
of  always  having  a large  supply  of  water,  so  that  they  could  be  kept 
constantly  wet. 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


33 


Cost  of  labor  would  be  about  . . . t . . . . $5,000 

Cost  of  building  the  furnaces  3 and  4,  and  condensers  now  in  use,  . 60,000 

Below  is  given  Knox  & Osborn’s  estimated  cost  of  a quicksilver 
furnace,  with  a capacity  of  75  tons,  or  to  work  24  tons  every  twenty- 
four  hours : 


Cast  iron  in  furnaces,  17,000  lbs.,  at  6 cts.  per  lb. 

j 

$1,020  00 

Cast  iron  in  condensers,  91,600  lbs.,  at  6 cts.  per 

lb.,  . . 

5,496  00 

Work,  planing  and  fitting,  .... 

. $90  00 

1 conical  charging  car, 

. 150  00 

1 discharging  car,  ...... 

. 125  00 

1 Knox  patent  suction  blower, 

. 400  00 

2 boxes  borings  to  caulk  condensers, 

. 10  00 

3 iron  kettles,  120  gallons  each, 

. 100  00 

Forging  bolt  ends,  and  nuts  and  screwing, 

. 70  00 

945  00 

Gross  amount  of  foundry  bill, 

$7,461  00 

20,000  feet  lumber,  at  $20  per  M,  . 

. 400  00 

80,000  red  brick,  at  $10  per  M, 

. 800  00 

7000  firebrick,  at  $60  per  M,  . 

. 420  00 

4000  lbs.  wrought  iron,  at  $5  per  M, 

. 200  00 

1 set  blocks  and  fall  (watch  tackle)  6 inches, 

. 10  00 

2 iron  sheaves,  1£  x 6 inches,  .... 

5 00 

4 iron  side  pulleys,  ..... 

2 00 

40  feet  chain,  1-inch  wire,  .... 

2 00 

10  kegs  nails  and  spikes,  at  $4.50  per  keg, 

. 45  00 

1,884  00 

Labor,  erecting  furnace,  .... 

. 

$2,000  00 

Boiler  and  engine,  four  horse-power, 

800  00 

$12,145  00 

In  this  estimate  nothing  is  included  for  grading  site,  drayage, 
freight,  hauling  brick,  sand,  clay,  rock,  and  timber,  to  the  furnace; 
nor  for  the  sheds  to  cover  the  structures.  As  different  sized  fur- 
naces would  require  about  the  same  amount,  as  an  approximation,  we 
may  say,  that  $3000  would  cover  an  extreme  case,  and  $1500  would 
suffice  for  a very  favorable  one.  In  a position  where  water  for  a 
four  horse-power  can  be  had,  a saving  in  the  first  cost  is  effected, 
and  a greater  saving  in  the  current  expenses  of  running. 

There  are  two  sizes  of  this  furnace,  a half  size,  or  12-ton  furnace, 
which  easily  treats  15  tons,  and  has,  when  crowded,  worked  17  tons. 

The  full  size,  or  24-ton  furnace,  crowded  in  the  same  way,  will 
work  30  to  34  tons. 


The  cost  of  the  half  size  furnace  is  about  . 

The  cost  of  the  three-quarter  size  furnace  is  about 


$9,000 

14,000 


Both  these  sizes  have  been  built  within  the  year  1874,  and  they 
are  giving  perfect  satisfaction. 


34 


NOTES  ON  THE  TREATMENT 


The  following  is  the  estimated  cost  of  running  or  operating  the 
Knox  & Osborn  furnace,  at  the  Manhattan  works,  per  day  of  twenty- 
four  hours,  when  run  by  steam  power : 

For  an  average  ore  for  24  hours,  1£  cords  of  wood  (oak),  at  $4.50  per 

cord,* . $5  63 

2 men  on  each  watch  of  twelve  houri,  or  4 men,  $50  per  month,  and 

board,  $2.53  per  day,  . 10  12 

Oil  for  light  and  engine, 50 

Cost  per  day  of  reducing  24  tons  of  ore,  ......  $16  25 

Cost  per  ton, 67f7 

With  regard  to  these  systems  of  working  it  may  be  said  that  the 
advantage  of  the  retort  system  is  its  economy  of  installation.  It 
does  not  appear  that  there  is  any  gain  in  yield,  though  this  is  claimed 
for  it,  while  the  expenses  for  fuel  and  labor  are  necessarily  a maxi- 
mum, as  the  amount  which  can  be  treated  at  any  given  time  must 
be  considered  as  a minimum.  The  cost  of  repair  is  also  a maximum, 
since  the  iron  of  the  retort  is  rapidly  attacked  by  the  sulphur  of 
the  ore,  which  destroys  them,  so  that  a larger  number  of  them  must 
always  be  kept  on  hand.  The  danger  of  accidents  from  salivation 
is  at  a maximum,  even  when  the  precaution  of  using  a blower,  as  at 
the  Missouri  mine,  is  taken,  and  there  seems  to  be  no  good  reason 
why  such  furnaces  should  not  go  out  of  use  altogether. 

There  is  evidently  a limit  beyond  which  the  speed  of  the  blowers, 
which  are  so  characteristic  of  California  practice,  cannot  be  increased. 
Not  only  is  a large  surface  necessary  to  a perfect  condensation,  but 
a certain  amount  of  time  is  quite  as  indispensable  to  cool  the  vola- 
tilized material,  in  order  to  have  it  condense.  If,  therefore,  the  con- 
densing surface  be  a maximum,  but  the  velocity  of  the  current  too 
great,  it  is  evident  that  there  will  be  a loss  of  mercury,  which  will 
be  exhausted  out  of  the  condensers  by  the  rapidity  of  the  current. 
The  proper  speed  of  the  blower  will  vary  at  different  times,  and 
with  the  obstruction  caused  to  the  passage  of  the  air,  by  the  kind  of 
condensers  used,  and  by  the  character  of  the  bre  charged  in  the  fur- 
nace. It  is  evident  that  in  a given  furnace,  the  ore  may  be  charged 
so  fine,  that  it  will  pack  in  such  a way,  that  no  speed  of  the  blower 
will  draw  the  furnace’s  gases  through  it,  or  so  large  that  a few  revo- 
lutions per  minute  will  be  all  that  will  be  required.  Between  these 
two  extremes  there  is  a mean,  which  can  only  be  determined  by  the 
judgment  of  the  person  in  charge  of  the  furnace,  and  it  is  often  pre- 

* Of  this  one  cord  would  lire  the  furnace,  one-quarter  the  boiler.  Ores  rich  in 
sulphur  will  not  require  over  one-half  cord  of  wood  in  twenty-four  hours. 


OF  MERCURY  IN  NORTH  CALIFORNIA. 


35 


cisely  this  judgment  and  skill,  which  may  or  may  not  have  been 
acquired  by  long  experience  with  a process,  which  makes  an  inferior 
process  give  good  results  in  one  place,  and  the  want  of  it  which 
makes  a good  process  fail  in  another.  Such  examples  occur  through- 
out the  whole  range  of  metallurgical  industry,  and  not  in  the  metal- 
lurgy of  mercury  only. 

The  objections  to  masonry  condensers  are  generally  the  penetrat- 
ing power  of  the  mercury,  which  is  so  great  that  it  not  only  impreg- 
nates the  vertical  stone  or  brick  walls  of  the  chambers,  but  infiltrates 
into  the  ground  to  such  an  extent  that  on  taking  up  the  the  founda- 
tions of  some  old  furnaces  at  New  Almaden,  about  the  year  1863,  mer- 
cury was  found  to  have  penetrated  through  the  foundation,  and  the 
clay  beneath  it  to  the  bed  rock  a depth  of  25  to  30  feet,  and  over  2000 
flasks  were  recovered  in  a single  year  from  the  foundations  of  two 
furnaces.  This  loss  is  now  prevented  by  building  the  condensing 
chambers  upon  double  arches,  into  which  plates  of  iron  are  built  so 
as  to  cut  off  the  flow  of  mercury,  and  turn  it  inwards  towards  an 
iron  basin  into  which  it  may  be  seen  to  fall  in  intermittent  streams 
every  few  minutes.  At  the  time  of  my  visit  to  New  Almaden 
a large  shaft  had  been  dug  beside  one  of  the  furnaces,  and  at  the 
depth  of  30  feet,  it  was  still  profitable  to  wash  the  dirt  in  order  to 
collect  the  mercury  from  it.  In  1874  sufficient  mercury  was  ob- 
tained from  the  brick  ore-chamber,  and  three  condensing-chambers 
of  a furnace,  and  from  the  dirt  around  the  structure,  to  more  than 
pay  for  the  new  shaft  furnace  and  condensers.  For  the  construction 
of  condensers  bricks,  though  porous,  are  much  preferable  to  and  I 
think  less  porous  than  the  sandstone  used  in  the  old  Idria  furnaces 
at  the  Redington  Works.  Whenever  repairs  in  the  condensers  at 
Knoxville  have  been  made  with  brick,  they  have  stood  while  the 
sandstone  next  to  the  bricks  has  been  worn  away.  It  is  evident 
that  what  is  required  is  some  substance  that  will  be  impervious  to 
mercury.  Bricks,  however,  are  not  so.  Every  brick  or  piece  of 
sandstone  taken  out  of  a condenser  must  be  considered  and  treated 
as  a very  rich  ore  of  mercury,  for  whenever  broken  myriads  of 
globules  of  metallic  mercury  are  seen  scattered  through  it.  Iron  is 
better  than  brick,  in  that  it  does  not  absorb  mercury,  but  it  is  rapidly 
corroded  by  the  sulphuric  acid  which  condenses.  Wood  is  much 
cheaper,  but  cannot  be  used  near  the  furnace  on  account  of  the  heat. 
At  a certain  distance  from  it,  it  is  more  or  less  rapidly  acted  on  by 
the  condensing  sulphuric  acid.  It  seems  perfectly  practicable  to 
make  such  a combination  of  wood  and  glass  that  will  stand  at  a 


36 


NOTES  ON  THE  TREATMENT 


certain  distance  from  the  fireplace,  and  by  placing  the  condensers 
made  of  brick  near  the  furnace,  and  cutting  them  up  into  smaller 
structures  so  that  they  shall  not  retain  the  heat,  or  substituting  iron 
condensers  with  water  cooling  arrangements,  for  them  to  arrange  a 
good  condensing  apparatus.  Jj3y  using,  for  instance,  the  Knox  con- 
densers together  with  the  wood  and  glass  arrangement  recently 
patented  at  Almaden,  it  would  seem  that  a much  better  condenser 
would  be  made  than  any  now  in  use.*  In  any  case  a few  large 
compartments  are  not  so  effective  as  the  same  volume  distributed 
among  a large  number  of  small  ones.  What  is  required  to  effect  a 
perfect  condensation  is  surface  more  than  volume,  and  more  especi- 
ally sudden  and  frequent  changes  of  the  direction  of  the  current  of 
volatilized  material.  With  a furnace  having  only  a natural  draft 
this  was  impracticable,  but  with  a furnace  working  by  an  exhaust 
fan,  where  obstacles  can  be  introduced  within  certain  limits,  it  is  only 
necessary  to  increase  the  speed  of  the  .fan  to  get  the  necessary  draft. 
There  is,  however,  evidently  a limit  of  obstruction  which  cannot  be 
overstepped. 

There  seems  to  be  a very  decided  advantage  in  using  an  artificial 
fuel  when  it  can  be  had ; European  experience  has  pronounced  de- 
cidedly in  favor  of  it.  At  Kew  Almaden  a series  of  experiments 
were  made  during  the  years  1873-4  with  coke  and  charcoal,  and  a 
mixture  of  both,  but  at  the  time  of  my  visit  no  definite  conclusion 
had  been  arrived  at.  It  would  seem  even  advantageous  under  certain 
circumstances  to  mix  a certain  amount  of  fuel  with  the  ore,  especi- 
ally when  large  amounts  of  fine  ore  not  made  into  adobes  must  be 
charged.  It  is  evident  that  the  fuel  which  contains  the  least  amount 
of  moisture,  if  it  is  not  friable,  will  prevent  the  formation  of  a 
certain  quantity  of  soot,  and  as  artificial  fuels  generally  contain  less 
moisture  than  natural  ones,  there  would  probably  be  less  acid  con- 
densed if  they  were  used.  There  are  places,  however,  where  the 
cost  of  making  the  artificial  fuel  would  more  than  counterbalance 
the  advantage  gained. 

Every  system  in  use,  and  some  which  are  not,  have  their  sup- 
porters. When  the  date  of  the  discovery  of  these  deposits  in  Cali- 
fornia is  taken  into  consideration,  it  must  be  confessed  that  more 

* While  this  paper  is  going  through  the  press,  Mr.  C.  E.  Livermore,  of  the 
Eedington  mine,  writes  that  they  have  commenced  to  use  six  or  eight  wooden 
condensers  to  each  furnace.  They  are  made  of  seasoned  red  wood  inches  thick, 
and  of  the  same  size  and  shape  as  the  iron  ones.  They  are  found  to  last  at  least 
equally  as  well,  and  are  far  cheaper. 


OF  MERCURY  OF  NORTH  CALIFORNIA. 


37 


rapid  strides  have  been  made  in  the  metallargy  of  quicksilver  there 
than  in  Europe.  There  is,  however,  much  to  be  done.  So  little  is 
known  of  what  is  done,  and  the  prices  of  the  metal  have  been  sub- 
jected to  such  great  fluctuations,  that  except  in  the  case  of  the 
wealthy  companies,  there  has  been  but  little  encouragement  to  ex- 
periment. The  price  of  quicksilver  in  San  Francisco  in  August, 
1874,  was  $1.75  per  pound.  It  is  now  75  cents,  and  has  been  in 
former  years  as  low  as  35  cents.  Such  prices  as  these,  if  they 
should  rule  again,  would  compel  almost  all  the  small  works  to  stop. 
The  general  feeling  is  that  every  advantage  must  be  taken  of  the 
present.  Under  such  circumstances  the  small  works  must  wait  to 
benefit  by  the  experiments  and  experience  of  the  larger  ones,  if  they 
are  not  entirely  ruined  by  the  fluctuations  in  value  before  they  have 
the  opportunity. 

In  conclusion,  I beg  to  express  my  thanks  to  Messrs.  C.  E.  Liver- 
more and  J.  W.  Hall,  of  the  Redington  mine,  and  to  Mr.  R.  F.  Knox, 
of  the  firm  of  Knox  & Osborn,  in  San  Francisco,  who  have  furnished 
me  photographs,  drawings,  and  a large  amount  of  information  before 
and  since  my  return  from  California,  and  to  the  managers  of  the 
works  generally  who  were  always  ready  to  facilitate  the  object  of  my 
visit. 


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Transactions  off  tin®  American  Institute  of  Mining  Engineers.  Vol.  III. 


PLANS  AND  SECTIONS  OF  THE  MODIFIED  IDRIA  FURNACES  Nos.  1 & 2 OF  THE  KNOX  FURNACES,  Nos.  3,  4,  B & 6,  AT  THE  REDINGTON  MINE,  NAPA  CO.,  CALIFORNIA. 


